unit 4

What three types of barriers are found in the innate immune system?

• Physical barriers

• Chemical barriers

• Mechanical barriers

When does the first line of defense activate, and how fast is it?

It reacts immediately as soon as a pathogen approaches the body's barriers.

• They act like a fence that is great for keeping most things out, but some things can still get through.

What are two main components of the first line of defense?

• Skin and mucous membranes

• Pattern Recognition Receptors (PRRs)

How does having no immunologic memory affect how innate immunity treats pathogens?

It reacts the exact same way to any potential pathogen from one exposure to the next.

What are the three types of cell-to-cell junctions in skin cells and their analog descriptions?

• Tight junctions: "Rivets" (vital in places like endothelial linings to keep microbes out of blood).

• Desmosomes: "Corset strings" (hold cells securely together).

• Gap junctions: "Channels" (gaps in between cells that are great for communication).

How do bacterial enzymes like proteases or hyaluronidase bypass cell junctions?

They degrade the junction proteins between cells, dissolving the barrier so pathogens can penetrate deeper.

1. Why is keratin in the skin epidermis an effective barrier against bacteria?

2. How does shedding skin cells and skin acidity help defend against microbes?

1. Bacteria cannot use keratin for food or break it down, severely limiting their available nutrients.

2. Sloughing cells: Dead cells constantly shed, carrying attached bacteria away with them.

3. Acidity: Acidic components in fats create an inhospitable environment because bacteria generally dislike acidity.

Where are mucous membranes located and what is their primary function?

• Locations: Nose, mouth, respiratory, digestive, and genitourinary tracts.

• Function: Secretes mucus to trap debris and microbes, protecting openings from foreign entry.

What is the mucociliary escalator and how does it function?

A defense mechanism where ciliated cells sweep mucus up and away from the lungs to be expelled from the body.

What is peristalsis and how does it act as a barrier defense?

Involuntary smooth muscle contractions in the intestines that physically move waste and undesirable microbes out of the body.

What is the definition of a mechanical defense in innate immunity?

Any sort of movement that actively pushes or flushes microbes away from the body.

What are five specific examples of mechanical defenses?

• Peristalsis / flushing action (elimination of urine and feces)

• Shedding of dead skin cells

• Mucociliary escalator sweeping trapped microbes away

• Tear and saliva production

• Blinking your eyes

What is the primary functional purpose of mechanical defenses?

To remove pathogens from potential sites of infection.

Into what two categories can chemical defenses be broken down?

• Endogenous mediators

• Exogenous mediators

What is the definition of an endogenous mediator?

Chemicals produced by your own body to help prevent infection.

Example:

Sebaceous glands- secrete sebum which seals off pore of hair follicle and helps create an acidic environment.

Salivary glands produce saliva (contains lactoperoxidase and lysozyme)

Stomach-HCI

Female reproductive tract-lactic acid lowers pH

What is the definition of an exogenous mediator?

Chemicals produced by your microbiome (the bacteria/microorganisms living in your body) to protect their habitat, which in turn protects you.

Example:

• Oleic acid: Lowers the pH of the skin.

• Microcin: Low-molecular-weight antibacterial peptides made by E. coli.

• Lactic acid: Produced by lactic acid bacteria to lower pH.

What are cytokines?

Chemical signals that cells use to talk to each other, secreted by immune cells to affect other cells.

What are Chemokines and what is their role?

• Cytokines that handle chemotaxis—they act like a GPS to tell white blood cells exactly where to go (recruiting them to infected areas).

• chemotaxis of immune cells

What are Interferons (IFNs) and what are they associated with?

Cytokines associated with viral infections. They alert cells, induce antiviral defenses, stimulate immune attacks on infected cells, and induce inflammation.

• control of viral infections, regulation of inflammatory response

What are Interleukins (ILs) and what was unique about their discovery?

• Cytokines produced by white blood cells that tell other white blood cells what to do. They were the first type of cytokine to be discovered.

• produced by leukocytes; important in innate and adaptive immunity

What are PRRs and what do they do?

• Definition: Pattern Recognition Receptors.

• Role: Special receptors on host cells that belong to the innate immune system and recognize signs of microbial invasion ("bad things").

What are PAMPs and who produces them?

• Definition: Pathogen-Associated Molecular Patterns.

• Source: Produced only by microbes (bacteria, viruses, fungi), never by the host. They are the target structures that PRRs recognize as bad.

• PAMS are like peptidoglycan, human cell don’t have peptidoglycan,

• - they are the bad things

What are Toll-like receptors (TLRs)?

Type oF PRR that are going te be found on sentinel cell (cell swimming around in you blood Stream) they are going to go and attack if they come into Contact with Some body (Micro-organism) it on site.

• TLR are found on macrophages and dendritic and they are going to do do phagocytosis when receptor bump in to PAMP

  * are going to be on the membranes

NOD-like receptors (NLRs)

receptors are going to be on cytoplasm ; bumps into bacteria, they then form an inflamm zone that inflammasome triggered the immune response.

• They form an inflammasome, which activates a strong inflammatory response and signals for more immune cells to come and help.

RIG-like receptors (RLRs)

are in cytoplasm different this this one is looking for viruses.

• is going to detect typically RNA vruses

• is going to release specifically and interfere on thing that we used to communicate a Cutokon is going to signal the cell around to come help the cells around it are going to release inactive antiviral proteins so they can make the cell do apoptosis.

What is the Complement System and why is it considered part of the innate immune system?

• Definition: A system of different proteins that are constantly present in your bloodstream.

• Innate Classification: Because these proteins are always there, they are considered part of the innate immune defenses.

What is a Complement Cascade and what happens at the end of it?

• Cascade: An activation chain reaction created when complement proteins bump into each other.

• End Result: It creates products that help defend the body against invading pathogens.

How many different pathways can stimulate the complement cascade?

Three different ways

• Classical pathway

• Lectin pathway

• Alternative pathway

Alternative Pathway

• C3 is going to spontancous|l Switch From C3A to C3B all the time.

• once C3 whether it's C3A or C3B bumps into a bacteria it is going Stay C3B. Once C3B is made it is then gonna Stimulate the cascade

Lectin pathway

During a bacterial infection, your liver produces mannose-binding lectin (MBL). That MLB is come into contact with C4. After MLB come in contact with c4 casacas.

Classical pathway

antibody binds antigen form the antibody, antigen complex. once this, complex bumps in the C1, cascade

Effects of Complement Activation

Opsonization, or immune adherence: enhanced phagocytosis Membrane attack complex: cytolysis

Induced Inflammation.

They are going to help stimulate make more the

Phagocytosis

What are complement proteins, where are they made, and how many are there?

They are a system of around 30 serum proteins produced by the liver. They circulate through the blood and tissues in an inactivated state.

What is Opsonization in complement activation, and which specific proteins are involved?

Certain complement proteins called opsonins (C1q, C3b, C4b) coat the foreign pathogen so phagocytes can easily find and eat them.

They act like tags or flags that attach directly to the bacteria.

How does complement activation lead to Inflammation, and which component triggers it?

C5a is activated, leading to the migration of neutrophils and other white blood cells (WBCs) to the infection site.

Neutrophils are stimulated by C5 to "know where to go" and are the first cells on the scene.

How does Cytolysis occur via the complement system?

Complement proteins C6–C9 are called in to form a Membrane Attack Complex (MAC), which creates holes in Gram-negative cell walls to destroy the bacteria.

Membrane attack proteins punch holes into the cell, causing it to die

What is Hematopoiesis

The process of making blood cells. All formed elements of the blood arise by differentiation of stem cells in the red bone marrow.

What is a Hematopoietic stem cell and where is it found?

A precursor cell found in the red bone marrow that has the potential to differentiate and turn into any type of blood cell the body needs. They typically stay in the bone marrow until they mature.

What are the scientific/medical names for RBCs, WBCs, and Platelets?

• RBC (Red Blood Cell): Erythrocytes

• WBC (White Blood Cell): Leukocytes

• Plats (Platelets): Thrombocytes

Mononuclear Phagocytes

• Macrophages, dendritic cells differentiate from monocytes

• are the precursors to macrophages Cells and dendritic they aren't going to have no nuclei and they can do phagocytosis

  - type of

  White blood cells

What are Granulocytes?

A category of white blood cells that contain cytoplasmic granules. This group includes neutrophils, eosinophils, and basophils.

Released histamine immune response

What is the primary function of Neutrophils

They engulf and destroy bacteria and other foreign material.

They are the 1st on the scene when there is some sort of cut or injury on the skin.)

What is the primary function of Basophils and Mast cells?

They are involved in allergic reactions and inflammation. Basophils circulate in the blood, while mast cells are similar but found fixed in tissues.

What is the primary function of Eosinophils?

They fight parasitic worms and are also involved in allergic reactions.

Macrophages

they do phagocytosis, they live in your body for week and months

Phagocytes can come together and make giant cell.

Neutrophils

• short life span of 1-2 days in tissues

• neutrophil extracellular traps

  The are going to be more powerful than macrophages, they can commit Sudoku and they release their DNA and then when they their release DNA it makes a net and that net can be use to trap bacterial or microbes

What is the primary role of Dendritic Cells, and what is their nickname?

They function as "scouts" (sentinel cells). They engulf material in tissues and bring it to the cells of the adaptive immune system for "inspection."

They come from monocytes, do phagocytosis, and go out to tell the rest of the immune system what to look for.

What are Lymphocytes responsible for, and what are the main types?

They are responsible for adaptive immunity. The group includes B cells and T cells (highly specific in antigen recognition, residing in lymph nodes/lymphatic tissues) and Natural Killer (NK) cells (which lack specificity).

They are going to go out and merge cells

What determines whether a Natural Killer (NK) cell will attack or spare a target cell?

NK cells are inhibited by the presence of Major Histocompatibility Complex (MHC I) receptors on healthy cells. If MHC I is missing or reduced, the NK cell kills the abnormal cell.

NK cells release chemicals that cause the target cell itself to die.

What is MHC I, and how does it function according to your notes?

MHC I is a protein displayed on cell membranes that allows cells to present antigens. It helps the immune system determine if a cell is self or non-self.

Flag Pole = MHC I. On that flagpole, cells display a flag: 1 = "I am healthy" or 2 = "I am sick". The antigen is the flag.)

Phagocytosis is primarily executed

by neutrophils, macrophages, and dendritic cells.

What happens during Step 1: Chemotaxis of phagocytosis?

Phagocytes are recruited to the site of infection by chemoattractants like chemokines, C5a, microbial products, or phospholipids from injured cells.

Phagocytes navigate there due to cytokines released by nearby cells.

What happens during Step 2: Recognition and Attachment?

Phagocytes bind to the invader. This can be direct (receptors binding directly to mannose on the microbe) or indirect(binding to opsonins coating the invader).

The macrophage must bump into receptors and connect to recognize what the bacteria is.

What happens during Step 3: Engulfment?

Pseudopods (surrounding extensions) encircle the foreign object and fuse to form a vesicle called a phagosome.

Once receptors bind, the cell engulfs the bacteria, bringing it inside the phagosome vesicle.

What happens during Step 4: Phagosome Maturation and Phagolysosome Formation?

The phagosome matures as endosomes fuse with it, lowering its pH. Lysosomes then fuse with the phagosome to deliver digestive enzymes, forming a phagolysosome.

How are pathogens destroyed during Step 5: Destruction and Digestion?

• Toxic ROS (reactive oxygen species) and nitric oxide are produced.

• The pH drops even lower.

• Lysosomal enzymes degrade the components.

• Defensins damage the invader's membrane.

• Lactoferrin sequesters (ties up) critical iron

Why does the phagocyte intentionally keep the most virulent (antigenic) parts of the destroyed pathogen instead of destroying everything?

It saves those specific pieces to display them on MHC II receptors so the adaptive immune system can learn to recognize the threat.

What happens during Step 6: Exocytosis?

The residual vesicle fuses with the cell's outer membrane to expel and discard the remaining waste material.

What is the overarching purpose of the inflammatory response?

To recruit necessary immune cells to the site of infection or injury, locate the threat, eliminate it, and begin tissue repair.

What are the cardinal signs/results of inflammation?

• Redness

• Heat

• Swelling

• Pain

• Loss of function (sometimes)

Pattern Recognition Receptors (PRRs) In inflammation

Structures are going to be responsible for triggering your TLR, NLR

Detect PAMPs, DAMPs

• PAMPs: Molecules found on invading pathogens (bacteria, viruses).

• DAMPs: Molecules indicating host tissue damage or distress signals.

* Host call, ralease inflammatory mediators (CYtokines, histamina, bradykinin)

• Inducers include microbes, tissue damage

• If blood vessels damaged, two enzymatic cascades activated; lead to coagulation and increased permeability

What causes the heat and redness during inflammation?

• The inflammatory response is also gonna be the cascade like compliment system.

The dilation of small blood vessels, which increases blood flow to the area but slows down the overall flow rate.

What causes the swelling and pain during inflammation?

Leakage of fluids out of the permeable blood vessels and into the surrounding tissues.

Describe the two-step process of Leukocyte Migration from the bloodstream into infected tissues.

1. Margination: Endothelial cells "grab" passing phagocytes to slow them down.

2. Diapedesis: The phagocytes squeeze between the cells of the blood vessel wall to enter the tissue.

What is pus, and why does it form at an infection site?

An accumulation of dead neutrophils, tissue debris, and fluids left behind after white blood cells rush to the scene to fight off invaders.

What organ controls body temperature, and what is its normal setting?

• The Hypothalamus controls body temperature and is normally set at 37°C.

  Fever is a normal, active part of your body's immune response.

what are the two main purposes of a fever?

1. To stop bacterial growth: Moving body temperature above the 37°C optimum causes bacterial growth rates to drop sharply.

2. To boost defenses: White blood cells (WBCs) are produced and work quicker at higher temperatures, allowing more time for defenses.

What is the difference between an Endogenous pyrogen and an Exogenous pyrogen?

• Endogenous pyrogens: Cytokines (like IL-1, IL-6, TNF) made by your own body's immune cells(macrophages/leukocytes) to tell the body to heat up.

• Exogenous pyrogens: External, foreign substances produced by microbes (such as Gram-negative LPS) that introduce a threat.

Describe the biological chain reaction that triggers a fever after an infection.

1. Gram-negative exogenous endotoxins cause phagocytes to release interleukin-1 (IL-1).

2. Cytokines tell the Hypothalamus to release prostaglandins.

3. Prostaglandins reset the hypothalamus to a higher temperature.

4. The body increases its metabolism and shivers to raise the physical temperature.

What causes body temperature to fall back down during a fever "crisis"?

Vasodilation and sweating.

How does a moderate rise in body temperature affect immune enzymes and responses?

It increases the rates of protective enzymes, which enhances the overall inflammatory response and boosts phagocytic killing by leukocytes.

What cellular behaviors are amplified or accelerated by a moderate fever?

• Multiplication of lymphocytes

• Release of attractants for neutrophils

• Production of interferons and antibodies

• Release of leukocytes from the bone marrow

What are the specific advantages of fever listed on your slide?

• Increases transferrins (iron-binding proteins that deprive bacteria of nutrients)

• Increases IL-1 activity

• Produces interferon

• Produces more WBCs (White Blood Cells)

What are the dangerous disadvantages and complications of a severe fever?

• Tachycardia (: Heart rate is going to go faster)

• Alkalosis

• Dehydration

• Temperatures of 44–46°C (111–115°F) are fatal

What are Interleukins and Cytokines, and what is their primary function?

They are molecular signaling proteins that serve as the immune system's primary network : Interleukin → Cytokine →how cells talk to each other

What is Adaptive Immunity, and what is its defining characteristic?

It is the second part of immunity that provides a highly specific and effective way to target threats that have been encountered before.
(It is going to remember things).

Describe the Primary response of adaptive immunity, including its timeline.

The first encounter with a specific pathogen or vaccine. It requires more work and takes 7 to 10 days to activate long-lived memory cells that specifically recognize the antigen.
(This is the response you have the very first time you come into contact with a particular pathogen; it takes time to develop that memory).

Describe the Secondary response of adaptive immunity and its clinical outcome.

A highly specific, immediate, and powerful response that occurs upon subsequent exposure to a pathogen the body has seen before. Because it acts so rapidly, it often results in no illness period.
(It is going to be more immediate because your adaptive system provides an immediate response to a pathogen it has already seen).

What are BCRs and how do B cells process foreign antigens?

B-cell are going ( BCRs) interact directly with foreign antigens. The B cell then internalizes the antigen and presents / displays it on MHC II molecules.( B cells, dendritic cells, and macrophages are the main antigen-presenting cells that do this).

Bcells are gonna give rise to plasma cells Plasma cells or antibiotic

What are TCRs, and what unique things they do

T cells are the second most widely used cells in your immune system, and T cell are going

To have T cells receptors, also going to

display antigen but only on MHC I

What is the primary focus and mechanism of Humoral Immunity?

It focuses on B cells and the production of antibodies to combat threats.
(B cells ultimately give rise to plasma cells which secrete antibodies).

B cells mature in the bone marrow and mature cells are found mainly in the blood and lymphoid organs.

What is the primary target and cell type responsible for Cellular Immunity?

It is driven by T cells and deals with intracellular (intercellular) antigens.
(Think of this as dealing with a "sick cell"—a host cell that is infected, sick, or damaged. T cells execute the cell-mediated response by recognizing these internal flags).

Where do T cells mature, and where are they primarily found afterward?

They mature in the thymus and are later found mainly circulating in the blood and lymphoid organs.

Contrast the core message of a Humoral response vs. a Cellular response based on your notes.

• Humoral: "A free-floating bacterium is here, B cells come do something about this!"

• Cellular: "An internal cell is displaying a flag saying 'I am infected, someone help me/destroy me,' and T cells respond to that."

What does the word Antigen literally mean, and what is its function?

Short for antibody generator, it describes a molecule that binds specifically with an antibody, a BCR, or a TCR.
(Antigens are unique molecular markers that all cells and biological entities possess).

• *Antigens =immunagenss

What are Self-Antigens vs. environmental hypersensitivity antigens (like pollen/dust)?

• Self-Antigens: Markers on your own healthy cells that your immune system should deliberately ignore.

• Pollen/Dust Antigens: Harmless environmental foreign particles that your body might accidentally over-respond to (causing allergies).

What does it mean if an antigen is T-dependent, and how common are they?

It means a B cell cannot act alone; it must first present the antigen to a helper T cell (\(T_{H}\)) to get confirmation before it can build antibodies. Most antigens are T-dependent.
(The antigen needs to be handed over to a T cell before a B cell can do anything with it).

What are T-independent antigens, and what are some examples?

Antigens that can activate B cells directly without needing helper T cell confirmation. Examples include lipopolysaccharide (LPS) and molecules with repeating sugar subunits (carbohydrates).
(The B cell can see the antigen and immediately get straight to business on its own).

What are epitopes (also called motifs)?

They are the specific parts or structural features on an antigen that an antibody recognizes and binds to.
( Antigens can be covered in many different epitopes, and some are more virulent or problematic than others.)

Antigen can be everywhere on a bacteria.

How do microbes use epitope switching to their advantage?

Some organisms can alter or switch out their surface epitopes, which acts as a virulence factor by helping them evade detection by the host's immune system.

What is another term for an antibody, and what cell type produces them?

They are also called Immunoglobulins (Igs), and they are specialized proteins produced by activated B cells (plasma cells).

What is the function of the Variable region of an antibody, and where is it located?

It is located at the tips of the Y-shaped molecule (Fab region) and provides the unique structural specificity for binding to a specific antigen.

What is going to Change between Classes gonna to be this variable region.

What is the function of the Constant region of an antibody?

It forms the stem of the antibody (Fc region). It is identical for all antibodies within the same class and is recognized by matching receptors on leukocytes.

What does Fab stand for, and what is its role?

Fragment of Antigen Binding. It is the top portion of the antibody responsible for directly grabbing onto the microbial motif.

What does Fc stand for, and what is its role?

Fragment of Crystallization. It is the base stem that sticks out to bind with Fc receptors on your own immune system cells.

(The variable is where the antibody antigen binding is what is happen Fragment of Crystallization or FC region is gonna be the part of the antibody that is sticking out FC are going to bind to other FC receptors on you immune system)

What are the five major classes of Immunoglobulins (antibodies)

• IgM (Mu)

• IgG (Gamma)

• IgA (Alpha)

• IgD (Delta)

• IgE (Epsilon)

Rank the five antibody classes in order of abundance from most abundant to least abundant.

1. IgG (Most Abundant / MA)

2. IgA

3. IgM

4. IgD

5. IgE (Least Abundant / LA)

What types of targets does Humoral Immunity defend against?

Extracellular antigens found in extracellular fluids.
(These are antigens not made by you, such as free-floating bacteria, fungi, and viruses).

IgG

accounts for 80–85% of total serum immunoglobulin (the most abundant class)

• Protect via neutralization, aggregation, opsonization, complement activation, and antibody-dependent cellular cytotoxicity

• • Transported across placenta to fetus's bloodstream

• they're gonna be used for just about all the way that anti bodies are going to function in your body

• main players when it comes to antibody functions they do it all

IgM

5–13% of circulating antibodies (the third most abundant). It is the first class produced during a primary immune response

It is a pentamer made of five monomeric subunits, giving it 10 antigen-binding sites aggregate them very effectively.

The classical pathway of the complement system. (It is great for initiating the classic cascade).

Production begins at birth