Lecture 1: Introduction to Immunology

prevent, eradicate

The most important physiologic function of the immune system is to ________ or _________ infections

Immunity

the ability to respond to pathogens and non-infectious substances

-environmental molecules, tumors, and unaltered host components

-clears damaged tissue

Immune System

the molecules, cells, tissues, and organs that collectively function to provide immunity, or protection, against foreign pathogens and cancers

-think of it like a symphony

Immune Response

a collective and coordinated response to the introduction of foreign substances in an individual mediated by the cells and molecules of the immune system

infections, tumors, self, regeneration, injure

The roles of the immune system include:

1. Defense against _________, which is the biggest and most principle role. This is why we give vaccines.

2. Defense against ________

3. Differentiate ____ from foreign, important for organ transplants

4. Control of tissue _________ and scarring, repairing/clearing damaged tissue

5. Immune system can ______ cells and induce pathologic inflammation, auto-immune disorders / allergies

Innate Immunity

initial protection, immediate and present in all healthy individuals

-natural/native, phylogenetically older than adaptive

-mediates inflammatory response

-non-specific

-no memory

Adaptive Immunity

develops more slowly, specific and has memory

-can recognize unique antigens on invading pathogens

-subdivided into humoral (extracellular infections) and cell-mediated immunity (intracellular microbes)

First

The innate immune system is the ____ line of defense. Has physical and biochemical barriers

-physical = skin, mucosa

-biochemical = secretions, saliva, GI tract

Second

Inflammation is the ______ line of defense, mediated by cellular influences

Third

Adaptive immunity is the ______ line of defense. It has a specialized response and memory for future infections

recognition, innate, adaptive, antibody, memory

The components of innate and adaptive immunity are:

1. Innate microbial _______

2. Induction of the _____ immune response

3. Activation of the ______ immune response

4. ______ production

5. Production of _________

Not

The innate immune response does ____ stop when the adaptive immune response is activated

Specificity

one of the characteristics of the adaptive immune system

out of millions of microbes, the immune system can recognize one single one

Clonal Selection Hypothesis

-tons of clones are derived from a common lymphocyte precursor cell

-the body selects one clone based on what it needs and makes tons of copies

Primary Response

the phase of the immune response where the naive lymphocytes are seeing an antigen for the first time

-leads to the production of plasma cells and memory B cells

Secondary Response

the phase of the immune response where memory lymphocytes recognize the antigen and is able to mount a larger, more specific attack

Lymphocytes

specific recognition of antigens and generation of adaptive immune responses

-B Lymphocytes = mediators of humoral immunity

-T lymphocytes = mediators of cell-mediated immunity

Antigen Presenting Cells

capture antigens for display to lymphocytes, function in innate immunity and as a bridge to adaptive immunity

-dedritic cells, macrophages, B lymphocytes

Neutrophils (PMN)

most abundant leukocyte in the blood

-phagocytic, acute inflammatory response to bacterial infection

Natural Killer Cells

target infected, stressed, or dying cells

-secrete interferon gamma

Mast Cells

derived from bone marrow, found in skin and mucosa

-involved in complement (innate immunity) and helminth infection or allergies (adaptive immunity)

B Lymphocytes

required for humoral immunity, produces antibodies

key mediators: promote phagocytosis, complement activation

T Lymphocytes

required for cell-mediated immunity

-broken up into CD4+, CD8+, and regulatory T cells

CD4+ T-Cells

recognize peptide fragments, help body produce antibodies, help eat microbes, and help with inflammation

CD8+ T Cells

also known as cytotoxic T cells

-identify and kill cells

Regulatory T Cells

help limit and prevent the activation of the immune response once infection has been cleared, helps prevent auto-immunity development

Humoral Immunity

Microbe: extracellular microbes

Responding Lymphocytes: B lymphocytes

Effector Mechanism: secreted antibody

Functions: block infections and eliminate extracellular microbes

Cell-Mediated Immunity

Microbe: phagocytosed microbes in macrophages or intracellular microbes replicating within infected cell

Responding Lymphocytes: Helper T lymphocytes or Cytotoxic T lymphocyte

Effector mechanism: activated macrophage or killing infected cell

Function: eliminate phagocytosed microbes, kill infected cells and eliminate reservoirs of infection

Cytokines

cell signaling molecules, important for communication

-interleukins, interferons, or tumor necrosis factor

Interleukins

secreted primarily by macrophages and lymphocytes, action varies depending on target cell

-plays a role in inflammation or anti-inflammatory, depending on target cell

Interferons

modulate inflammatory response, activate innate immune cells

-interfere with viral infections

Tumor Necrosis Factor

secreted by macrophages and T-cells

-helps with proliferation, differentiation, apoptosis

Chemokines

family of low molecular weight peptides that function primarily in leukocyte chemotaxis, which is the movement of leukocytes from blood into tissues and maintain cell organization

Bone marrow

What generative lymphoid organ houses B lymphocytes?

Thymus

What generative lymphoid organ houses T lymphocytes?

Peripheral Lymphoid Organ

spleen, lymph nodes, and mucosal/cutaneous lymphoid tissues

-encounter antigens, recognize, receive signals to proliferate/mature/differentiate

Precursor, organ, circulation, organs

T and B Cells mature following this path:

1. Common lymphoid ________

2. Move to the generative lymphoid ______. The immature B lymphocytes are in the bone marrow, and the mature naive T lymphocytes are in the thymus.

3. The cells then move into _______.

4. Cells can go to the peripheral lymphoid _______, like the spleen and lymph nodes.

5. They then become mature and can recirculate between the organ and blood.

Memory, naive

At a young age, humans have more naive T cells than _________ T cells. This shifts as you age and encounter antigens, eventually the production of memory T cells compensates for the decline in ____ T cells.

Bone marrow, thymus

Central lymphoid organs

lymph nodes, spleen, cutaneous and mucosal systems

Peripheral lymphoid organs

Lymph Nodes

collection of lymph tissues along lymphatic channels throughout the body

-drains lymph

-B-Cells arranged into follicles along the exterior

-T cells localized to central portion

Expert filters

Lymph nodes are _____ _____. This process is really slow, APCs sample fluid for microbes that may have entered the lymph.

Lymph nodes

Which peripheral lymphoid organ has the most lymphocytes?

Right Lymphatic Duct

drains the right side of the head, right arm, and right side above the diaphragm

-located below the right subclavian vein

Thoracic Duct

drains the entire left side of the body, also the right side below the diaphragm

-located below the left subclavian vein

Spleen

peripheral lymphoid organ that helps clear old red blood cells, provide immune responses to blood borne pathogens, and are lined with phagocytes

Cutaneous and Mucosal Systems

specialized collections of lymphoid tissues

Peyer’s Patches

found in the GI tract

-specialized collection of lymphoid tissue that resembles a lymph node, contains APCs and other cells

Tonsils

found in respiratory tract

-specialized collection of immune cells found in the respiratory tract