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MCAT-BIOLOGY > Immune System > Flashcards

Immune System Flashcards

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1
Q

what are the three types of immunity?

A

innate (general), humoral (specific, B cells/antibodies), cell-mediated (specific, T cells/killers)

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2
Q

innate immunity

A

general, nonspecific protection of the body against various invaders, rapid (ex. skin, lysozyme, acidity, macrophages/neutrophils, complement system that can nonspecifically bind foreign cells for destruction)

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3
Q

humoral immunity

A

specific protection by antibody proteins (immunoglobulins) that specifically recognize and bind to microorganisms leading to their destruction and removal from the body

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4
Q

what is the structure of antibodies?

A

two copies of both light chains and heavy chains joined by disulfide bond, contains a constant region (defines antibody class, ex. IgG, IgA, IgM, IgD, IgE) and variable region (antigen binding region)

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5
Q

IgM

A

found in blood and B cell surface, involved in initial immune response, pentameric structure in blood, monomeric structure on B cell as antigen receptor

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6
Q

IgG

A

found in blood, involved in ongoing immune response, the majority of antibody in the blood is IgG, can cross the placental barrier

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7
Q

IgD

A

found on B cell surface, serves with IgM as antigen receptor on B cells

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8
Q

IgA

A

found in secretions (saliva, mucus, tears, breast milk), secreted in breast milk; helps protein newborns, dimeric structure

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9
Q

IgE

A

found in blood, involved in allergic reactions

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10
Q

antigen (Ag)

A

the molecule that an antibody binds to

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11
Q

what determines the specificity of antigen binding?

A

the fit of antigen in a small three-dimensional cleft formed by the variable region of the antibody protein

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12
Q

epitope

A

the small site that an antibody recognizes within a larger molecule (i.e. an antigen can have multiple recognition sites for different antibodies)

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13
Q

can very small molecules elicit antibody production?

A

no, unless bound to an antigenic large molecule in which the small molecule becomes antigenic and is known as a hapten

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14
Q

when are the 3 possible outcomes when an antibody binds to an antigen?

A

1) directly inactivate the antigen (ex. can’t bind or enter cells)
2) induce phagocytosis by macrophages and neutrophils
3) antibodies on surface can activate the complement system to form holes in the cell membrane and lyse the cell

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15
Q

primary immune response

A

the first time a person encounters an antigen during infection, in which there is a time interval for B cells to proliferate and secrete antibodies

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16
Q

secondary immune response

A

swifter and stronger than primary immune response, symptoms don’t develop, B memory cells become activated and start producing antibodies

17
Q

clonal selection

A

method of selecting B cells (or T cells) with specific antigen binding

18
Q

what are characteristics of B cells?

A
  • immature B cells derived from stem cells in bone marrow
  • genes encoding antibody proteins assembled by recombination, so many different B cell clones with different variable regions exist
  • immature B cells express antibody molecules on the surface
  • when antigen binds to antibody, immature cell is stimulated to proliferate and differentiate into plasma cells (actively produce and secrete antibody proteins) and memory cells (pre-activated, dormant B cells with antibody on membrane surface)
  • actually activated by T helpers that recognize MHCII and release cytokine factors (lymphokines and interleukins) that activate B cell proliferation
19
Q

vaccination

A

used to improve the response to infection by exposing the immune system to an antigen associated with a virus or bacteria, thus building up the secondary immune response if the live pathogen is encountered in the future

20
Q

what are the two types of t cells?

A

T helpers (CD4-associate with alarm, MHCII) and T killer (cytotoxic T cells, CD8 cells, MHCI)

21
Q

where to T cells develop?

A

derived from bone marrow but develop in the thymus during childhood (thymosin hormone)

22
Q

what is the role of T killer cells?

A

to destroy abnormal host cells

23
Q

characteristics of T cells

A
  • antigen-binding site is specific and also formed from recombination
  • recognizes cell by binding to both the antigen and MHC complex
24
Q

major histocompatibility complex (MHC)

A

cell-surface proteins that are recognized and monitored by the immune system for foreign agents in the cell, two types (MHCI and MHCII)

25
Q

MHC I

A

found on the surface of every nucleated cell, randomly picks up peptides from inside of the cell and displays them on the cell surface, specifically recognized by T killer cells

26
Q

MHC II

A

only antigen-presenting cells (APC’s) have MHCII, including macrophages and B cells which phagocytize particles or cells and displays fragments, recognized and bound by T helpers which then activate B cells and T killer cells

27
Q

bone marrow

A

the site of synthesis of all cells of the blood from a common progenitor

28
Q

spleen

A

filters the blood and is a site of immune cell interaction (similar to lymph nodes), also destroys aged RBCs

29
Q

thymus

A

site of T cell maturation, shrinks in adults, most active in children

30
Q

tonsils

A

masses of lymphatic tissue in the back of the throat that help to catch pathogens which enter the body through respiration or ingestion

31
Q

appendix

A

similar to tonsils, mass of lymphatic tissue at the beginning of the large intestine that help to catch pathogens

32
Q

why are the tonsils and appendix often removed?

A

because both are not required for survival and can become infected

33
Q

tolerance

A

ability of the immune system to only recognize and destroy foreign antigen while ignoring all normal proteins and cell structures

34
Q

how to ensure B cells and T cells don’t destroy own cells?

A

recombination can produce self antigens, thus a selection process is undergone to eliminate any self-reactive cell. selection present in the bone marrow and lymph nodes, if binds to normal cell surface proteins (apoptosis) or bind to normal soluble proteins (unresponsive, anergic)

35
Q

B cell or T cell clone

A

B or T cells that are identical and specific to a particular antigen, formed by proliferation stimulated by antigen in a specific context

36
Q

autoimmune reaction

A

immune system attacks normal body cells or proteins

MCAT-BIOLOGY (17 decks)

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