Lesson 2: (Continuation) Cells of the Immune System and Antigen Recognition

This immunity uses:

• Antibodies, produced by lymphocytes, circulating freely in body fluids

• Bind temporarily to target cell

– Temporarily inactivate

– Mark for destruction by phagocytes or complement

• has extracellular targets

Humoral immunity

This type of immunity

• Lymphocytes act against target cell

– Directly – by killing infected cells

– Indirectly – by releasing chemicals that enhance inflammatory response; or activating other lymphocytes or macrophages

• has cellular targets

Cellular immunity

Active or Passive immunity:

• Resistance acquired after contact with foreign antigens, eg, microorganisims

• This contact may consist of :

– Clinical or subclinical infections

– Immunization with live or killed infectious agents or their antigens.

– Exposure to microbial products (eg, toxins and toxoids)

Active immunity

Active or Passive immunity:

• is resistance based on antibodies preformed in another host.

• IgG= passed from the mother to the fetus during pregnancy.

• IgA= passed from the mother to the newborn during breast feeding.

Passive immunity

This immunity:

• involves giving both preformed antibodies (immune globulins) to provide immediate protection

• Vaccine to provide long term protection

• prevents: Tetanus, Rabies and Hepatitis B

Passive-active immunity

• Substances that can mobilize adaptive defenses and provoke an immune response

• Targets of all adaptive immune responses

• Most are large, complex molecules not normally found in body (non-self)

Antigens

What are the 2 types of substances that triggers an immune response or antibody formation?

Immunogen and Antigen

Immunogenic involves the use of ___ which are foreign molecules that are able to induce an adaptive immune response (antibody or T-cell production) in the body. they will stimulate immune cells and then give rise to immunological reaction (Humoral or cellular).

Immunogen

True or false:

Antigenic substances cannot directly yield immune response, but need some help by some proteins) and then they can react with antibodies.

True

___ ability to stimulate proliferation of specific lymphocytes

Immunogenicity

____ ability to react with activated lymphocytes and antibodies released by immunogenic reactions

Reactivity

• Small molecules not immunogenic by themselves (ex. peptides, nucleotides, some hormones)

• May be immunogenic if attached to body proteins and combination is marked foreign

• Cause immune system to mount harmful attack

• Examples: poison ivy, animal dander, detergents, and

cosmetics

Haptens

• Only certain parts of entire antigen are immunogenic

• Antibodies and lymphocyte receptors bind to them as enzyme binds substrate

antigenic determinants

True or false:

• Most naturally occurring antigens have numerous antigenic determinants that

– Mobilize several different lymphocyte populations

– Form different kinds of antibodies against them

• Large, chemically simple molecules (e.g., plastics) have little or no immunogenicity

True

Give an example of antigenic determinant

Epitope

True or false

• Epitopes are small chemical groups on the antigen molecule that can elicit and react with antibody.

• The antigen has variable number of epitopes and this is called the valency of the antigen

True

True or false:

Protein molecules (self-antigens) on surface of cells not antigenic to self but antigenic to others in transfusions or grafts

True

True or false

Example of self antigen: MHC glycoproteins

- Coded by genes of major histocompatibility complex (MHC) and unique to individual

- Have groove holding self- or foreign antigen

• T lymphocytes can only recognize antigens that are presented on MHC proteins

True

What are the 3 Properties of antigen ( Foreign substances) to be Immunogenic

1. Foreignness

2. Chemical-Structural complexity

3. Molecular size

What are the 3 categories of antigen( Foreign substances) to be Immunogenic under foreignness category

1. Autologous antigens

2. Allogenic antigens

3. Heterologous antigens

___ are self antigens derived from an individual's own tissues, cells, or DNA and there will be no immune response since the immune system is trained to recognize them as part of the body.

Autologous antigens

___ are antigens from the same species and there may be reaction

eg. Blood transfusion and kidney transplant.

Allogenic antigens

___ are antigens from different species. These antigens will be rejected and there will be severe immune response

Heterologous antigens

True or false:

Chemical-Structural complexity

• A certain amount of chemical complexity is required; eg. amino acid

• Homopolymers are less immunogenic than heteropolymers containing Two or three different amino acids

True

True or false:

Molecular Size

• The most potent immunogens are proteins with high molecular weight (above 100,000).

• Generally, molecules with molecular weight below 10,000 are weakly immunogenic, and very small ones eg an amino acid are non-immunogenic

True

___ word is from Latin means “aiding”and these are

immunopotentiating agents.

• These are of two types

• ( Ag+Ab)---→Injected---->Increased immune response

Adjuvant

True or false

Today, adjuvants play an important role in the efficacy of vaccines. Stimulating the correct immune response is a must when selecting an adjuvant to use for a new vaccine. Since one adjuvant alone is rarely optimal for all antigens, it is critical to have a selection of different types of adjuvants for evaluation with your antigen.

True

True or false:

Adjuvants are nonspecific stimulators of the immune response. When mixed with an antigen or immunogen, adjuvants help to deposit or sequester the injected material thereby helping to increase antibody response. Adjuvants enhance the immune response to compounds that are already immunogenic; they do not confer immunogenicity to non-immunogenic haptens.

True

What are the 6 different preformed receptors:

1. Pattern recognition receptors (PRR)

2. Toll-like receptors (TLR)

3. Killer activation receptors

4. Killer inhibition receptors

5. Complement receptors

6. Fc receptors

recognize patterns in antigens such as the presence of MHC class I molecule and checks antigens’ DNA and RNA

Simple Explanation: The immune system's "sensors" that look for general, non-self molecular patterns common to many pathogens (PAMPs) or damaged host cells (DAMPs)

Pattern recognition receptors (PRR)

from sentinels cells (macrophages, dendritic cells, and mast cells)

A specific, major family of PRRs located on the cell surface or inside endosomes that detect pathogens (like bacteria or viruses).

Toll-like receptors (TLR)

A receptor that trigger the NK cell to destroy infected, stressed, or tumor cells.

Killer activation receptors

Prevent Natural Killer (NK) cells from attacking healthy cells by identifying "self" markers (MHC Class I).

Killer inhibition receptors

A receptor that Recognize activated complement components in proteins (e.g., C3b, iC3b, C4b) that have coated a pathogen.

Function: Promote phagocytosis (engulfment), cell adhesion, and clearance of antigen-antibody complexes.

Complement receptors

A receptor that Recognize the constant (Fc) region of antibodies that are bound to pathogens.

Function: Trigger effector functions such as Antibody-Dependent Cellular Cytotoxicity (ADCC), phagocytosis, and release of inflammatory mediators.

Fc receptors

What are the 2 Somatically-generated receptors

1. B cell receptors (BCR)

2. T cell receptors (TCR)

What are the Anatomical Barriers - Mechanical Factors?

1. Skin

2. Mucociliary escalator

3. Flushing action of saliva, tears, urine

Anatomical Barriers – Biological factors?

• Normal flora – microbes in many parts of the body

• Normal flora – > 1000 species of bacteria

• Normal flora – competes with pathogens for nutrients and space

Anatomical Barriers – Chemical factors?

1. Antimicrobial Peptides in sweat

2. HCl in stomach

3. Lysozyme in tears /saliva

true or false: SKIN

• Microorganisms normally Associated with skin prevent Potential pathogens from Colonizing.

• Sebaceous glands secrete Fatty acids and lactic acid Which lower the skin pH (pH 4-6).

• Unbroken skin is a contiguous Barrier

• The skin has a low moisture content

True

True or false: MUCOSAL MEMBRANES

• Ciliated epithelial cells lining the trachea remove microbes inhaled through the nose and mouth.

• Mucus secreted by these cells prevent the microbes from associating Too closely with the cells

• Cilia push microbes upwards until they are caught in oral secretions and expectorated or swallowed.

True

True or false: GASTROINTESTINAL TRACT

• The pH of the stomach is 2.0 which is too low for most pathogens

• Pathogens must compete with the normal flora associated with the small and large intestines. (pH 5 and 7, respectively).

• The large intestines normally contain approx 1010 bacteria per gram of content—establishment of pathogens difficult

• Microbes have a difficult time adapting to abrupt changes in pH as they might encounter as they pass through the GI tract.

True

True or false: LYSOZYME (eye) & KIDNEY

• Lysozyme constantly baths the kidney and the surface of the eye (tears). Also found with egg whites and the female urogenital tract, and saliva)

• Lysozyme breaks the glycosidic bonds between the NAG and NAM that make up the backbone of peptidoglycan—causing bacteria to lyse.

True

True or false: EXTRACELLULAR FLUIDS

• Blood plasma contains bacteriocidal substances

• Blood proteins called beta-lysins bind to and disrupt the bacterial cytoplasmic membrane—leads to leakage of the cytoplasmic constituents and bacterial cell death

True or false: Tissue Specificity

• first adhere and colonize at the FIRST site of exposure. If this site is not compatible with their environmental or nutritional needs they die.

• EXAMPLE: Clostidium tetani—tetanus.

- Ingestion: The organism does not survive the low pH of the stomach.

- Introduced into a deep wound: organism can grow in this anoxic environment that has been created by localized tissue

True

True or false: inflammation

• Nonspecific reaction to stimuli such as toxins or pathogens.

• Mediated by a subgroup of leukocytes (white blood cells) that produce cytokines that lead to fibrin clots at the site of inflammation.

• The inflammatory response results in redness, swelling, heat and pain at the site of the infection

• Most important outcome is the immobilization of the pathogen at the site of inflammation

True or false:

Physical manifestations: Inflammation

• Abscess—localized collection of pus surrounded By a wall of inflammatory tissue (surface localized)

• Boils—abscesses located in the deeper layers of the skin

• Ulcers—localized area of necrosis of the epithelial cells

True

Uncontrolled systemic inflammatory responses causes severe swelling and fever—occurs when the infections and Inflammatory responses are not localized to one site

Septic Shock Syndrome

Hospital patients with noninfectious diseases acquire infections through invasive procedures like catheterization, biopsy, surgery, hypodermic injection etc.

Nosocomial infections—hospital acquired

True or false:

• Stress and prolonged exertion—production of hormones like cortisone that is an effective anti-inflammatory agent

• Diets low in protein alter the composition of the normal flora thus allowing opportunistic pathogens a chance to colonize

• Smoking—destroys or immobilizes cilia associated with the nasopharyngeal and tracheal regions

True