Introduction to Immunology

target of our immune system; agent that causes disease

antigen

What are the 3 main roles of the immune system?

defense against infections, recognition and response to foreign tissues and proteins, defense against tumors

Why are vaccinations so effective?

they stimulate an immune response to certain microbes and prime immune system for potential infection by those microbes

type of immunity that quickly mediates the initial protection against infectious agents; includes the first line of defense

innate

type of immunity that develops more slowly and mediates the long term, more effective defense against infectious agents

adaptive

When does innate immunity respond to a foreign agent?

within hours

When does adaptive immunity respond to a foreign agent?

requires days

What is the initial, first line of defense in innate immunity?

epithelial barriers

(physical barrier against infectious agents)

cells involved in innate immunity that are just underneath the epithelium and function to ingest microbes

phagocytes

Are natural killer cells part of innate or adaptive immunity?

innate

Is the complement cascade system part of innate or adaptive immunity?

innate

Why is it important that we have adaptive immunity? Why not just innate?

some microbes have evolved to resist innate immunity

What are the two main kinds of lymphocytes in adaptive immunity?

B cells, T cells

type of adaptive immunity that provides defense against extracellular microbes or foreign particles

humoral

type of adaptive immunity that provides defense against intracellular microbes (viral or phagocytosed)

cell mediated

Are B lymphocytes humoral or cell mediated?

humoral

Are T lymphocytes humoral or cell mediated?

cell mediated

What is the function of humoral immunity?

block infection and eliminate extracellular microbes

What is the function of cell-mediated immunity?

kill infected cells and activate other cells to kill microbes

What are the 3 most important properties of adaptive immunity?

specificity, diversity, memory

2 distinct antibodies can be produced from 2 distinct B cell populations (anti-X and anti-Y) against 2 different antigens (X and Y). This exemplifies which important characteristic(s) of adaptive immunity?

specificity, diversity

A second response to an antigen X can be produced by anti-X B cells that is much stronger than the primary response. This exemplifies which important characteristic(s) of adaptive immunity?

memory

response with a lower serum antibody titer since memory B cells have to be produced for the first time

primary

response with a higher serum antibody titer since memory B cells have already been produced

**so from now on, memory cells provide faster and more robust responses each subsequent time that the same antigen infects the body

secondary

theory stating that lymphocytes express clonally distributed receptors for antigens so that there are many individual populations of lymphocytes, each expressing a different antigen receptor

Basically, clones of lymphocytes specific for different antigens develop before an encounter with these antigens, and each antigen elicits an immune response by selecting and activating the lymphocytes of a specific clone.

1. Lymphocyte clones mature in generative lymphoid organs in the absence of antigens

2. Clones of mature lymphocytes specific for diverse antigens enter lymphoid tissues

3. Antigen-specific clones are activated ("selected") by antigens

4. Antigen-specific immune responses occur

clonal selection hypothesis

1/5 main phases of adaptive immune responses that involves recognition of an antigen by specific lymphocytes

recognition phase

2/5 main phases of adaptive immune responses in which cells, once recognized, are activated and start proliferating (clonal expansion) and differentiating into effector cells (which produce substances to eliminate antigen)

activation phase

3/5 main phases of adaptive immune responses that involves elimination of antigen (humoral & cell-mediated)

effector phase

4/5 main phases of adaptive immune responses that consists of eliminated antigen and dying/dead effector cells (apoptosis) and a return to homeostasis

**when the antigen is being cleared out, the immune response is weaker and weaker as we have less and less antigen

decline/contraction phase

5/5 main phases of adaptive immune responses that consists of the surviving antigen-specific cells (B and T) called memory cells

memory phase

Specificity is an important part of which system?

A. innate immunity

B. adaptive immunity

B

lymphocytes whose main job is to secrete antibodies, which help to neutralize microbes, stimulate phagocytosis, and stimulate complement activation

B cells

lymphocytes with many different types, including helper, cytotoxic, regulatory, and natural killer

T cells

T cells that activate macrophages and B cells

helper

T cells that kill any type of infected cell (mostly viral)

cytotoxic (cytolytic)

T cells that suppress the body's immune response against our own self cells

regulatory

T cells (technically) that kill infected cells (more involved in the innate response)

natural killer

category of phagocytic cells including macrophages, dendritic cells, and B cells that phagocytose an antigen, process it, and then express specific peptides of that antigen so that T cells can target it

antigen presenting cells

short-lived cells that take effect immediately against the antigen and any pathogens producing that antigen, including macrophages, T cells, B cells, and granulocytes (consisting of basophils, eosinophils, neutrophils)

effector cells

place of origination and maturation for B lymphocytes

bone marrow

place of maturation (only) for T lymphocytes

thymus

Once B and T lymphocytes mature in their respective organs, they can now migrate out of those organs and go to peripheral, or secondary, lymphoid organs, where they respond to foreign antigens and recirculate into the blood and lymph.

Even though they're mature, why are these cells considered "naive"?

they haven't encountered an antigen yet

Where do B and T lymphocytes first encounter antigens?

secondary lymphoid organs

Where are T cells found in the spleen?

periarterial lymphatic sheath (PALS, within white pulp)

Where are B cells found in the spleen?

follicles (within white pulp)

Where are T cells found in lymph nodes?

paracortex

Where are B cells found in lymph nodes?

follicles

Naive B and T cells migrate into lymph nodes via the bloodstream and become activated by antigens. Activated B and T cells then exit the nodes via both the bloodstream and lymph system, where they can then do what?

migrate to peripheral sites of infection

lymphoid tissue found in the small intestine (gut associated lymphoid tissue, GALT)

Peyer's patches

What are the 6 main forms/organs of secondary lymphoid tissue?

spleen, lymph nodes, Peyer's patches, appendix, tonsils, adenoids

Which two of the cells listed below are lymphocytes?

A. neutrophils

B. B cells

C. dendritic cells

D. macrophages

E. T cells

B, E

Specific immune responses...

A. require helper T-cell activation

B. are under control of the adaptive immune system

C. could not occur if the thymus gland did not develop

D. require recognition of antigens by receptors

E. all of the above

E