BIO205 Topic 5 Chapter 14 & 15

Innate Immunity & Adaptive Immunity

what is the difference between innate and adaptive immunity?

Innate: routine, immediate, non-specific, uses pattern recognition. Adaptive: develops through life, antigen-specific, produces antibodies, has memory

what are the components of first-line defense?

skin, mucous membranes, antimicrobial substances, normal microbiota

what does lysozyme do?

breaks down peptidoglycan in bacterial cell walls

what is the role of iron in immunity?

microbes need iron; lactoferrin binds iron to prevent microbial growth

what are surface receptors?

proteins that allow cells to sense and response to their environemnt

what are cytokines?

chemical messengers; the “voices” of the cell

what is tumor necrosis factor (TNF)?

a cytokine involved in inflammation

what do interferons (IFNs) do?

produced when viral RNA is detected; trigger antiviral defense in nearby cells

what do interleukins (ILs) do?

cytokines that coordinate immune responses between leukocytes

what is the role of normal microbiota?

competitive exclusion, produce toxic compounds, maintain low pH, prevent pathogen overgrowth

what do neutrophils do?

rapid responders; major phagocytes

what do basophils do?

release histamine; involved in inflammation and allergies

what do eosinophils do?

fight parasites; involved in allergic reactions

what do monocytes do?

circulate in blood; develop into macrophages

what do macrophages do?

phagocytosis; antigen-presenting cells

what are lymphocytes?

B cells, T cells, NK cells

what are TLRs?

Toll-like receptors; detect extracellular PAMPs

what are NLRs?

NOD-like receptors; cytoplasmic sensors; form inflammasomes

what are RLRs?

RIG-like receptors; detect viral RNA; trigger interferons

what is complement system?

serum proteins that enhance immunity; all pathways converge at C3

what is opsonization?

coating microbes to enhance phagocytosis

what are the functions of inflammation?

contain damage, eliminate invader, restore tissue

what are the cardinal signs of inflammation?

heat, pain, redness, swelling, loss of function

what is fever?

elevated body temperature as a defense mechanism

how is fever induced?

endogenous pyrogens (macrophages) + exogenous pyrogens (microbes) raise hypothalamic set point

what are pyrogens?

substances that cause fever

what is a phagosome?

vesicle containing an engulfed microbe

what is a phagolysosome?

fusion of phagosome + lysosome

what is a lysosome?

organelle with digestive enzymes that destroy microbes

humoral vs cellular immunity?

Humoral: B cells → antibodies; targets extracellular pathogens. Cellular: T cells; targets infected cells, cancer, transplants

what are B lymphocytes?

mature in bone marrow; produce antibodies

what are plasma cells?

activated B cells that secrete antibodies

what are memory cells?

long-lived cells that respond rapidly upon re-exposure

what are T lymphocytes?

mature in thymus; require antigen presentation

what is the T-cell receptor (TCR)?

recognizes antigen only when presented on MHC

what is MHC class I?

on all nucleated cells; presents endogenous antigens to CD8 T cells

what is MHC class II?

on APCs; presents exogenous antigens to CD4 T cells

what are T-cytotoxic cells (CD8)?

kill infected or abnormal cells using perforin + granzymes

what are T-helper cells (CD4)?

activate B cells, macrophages; coordinate immune response

what is CD4?

marker on helper T cells

what is CD8?

marker on cytotoxic T cells

what are dendritic cells?

professional antigen-presenting cells

what are APCs?

macrophages, dendritic cells, B cells

what are natural killer (NK) cells?

kill cells lacking MHC I or coated with antibodies

what is an antigen?

molecule that binds BCR, TCR, or antibody

what is an immunogen?

Antigen that triggers immune response. Strong = proteins, polysaccharides. Weak = lipids, nucleic acids

what are epitopes?

antigenic determines

describe antibody structure

Y-shaped; 2 heavy + 2 light chains; Fab (variable), Fc (constant)

what are the 5 antibody classes?

IgM, IgG, IgA, IgD, IgE

what is an immunoglobulin?

another term for antibody

what is a T-dependent antigen?

requires TH cell help; forms memory

what is a T-independent antigen?

polysaccharides, LPS; no memory

what does anergic mean?

B cell becomes unresponsive without TH cell help

what is clonal selection theory?

antigen selects matching lymphocyte → clonal expansion → effector + memory cells

what is gene rearrangement?

B cells rearrange V, D, J segments → antibody diversity

why is diphtheria toxin historically important?

led to discovery of antitoxin (antibody-based immunity)

what are primary lymphoid organs?

bone marrow, thymus

what are secondary lymphoid organs?

lymph nodes, spleen, tonsils, adenoids, appendix

what are the outcomes of antibody-antigen binding?

neutralization, opsonization, complement activation, agglutination, immobilization, ADCC