Roles of immune system component

Neutrophils

engulf and destroy the infecting pathogens

Macrophages

“big eaters”

Dendritic cells

stimulate adaptive immunity by encounter and engulf

Natural killer cells

do not engulf stricken cells and release chemicals that lead to cell death

Interferon

proteins provide innate defense, interfering with viruses and helping activate macrophages

Mast cells

a type of connective tissue, release histamine, which triggers blood vessels to dilate and
become more permeable

Activated macrophages and neutrophils

release cytokines, signaling molecules that enhance the immune response

effector B cells

short-lived, act immediately against the antigen

memory B cells

long-lived, give rise to effector cells if the same antigen is encountered again

Plasma cell

secrete antibodies specific for the antigen.

humoral immune response antibodies

help neutralize or eliminate toxins and pathogens in the blood and lymph

cell-mediated immune response

T cells destroy affected host cells

cytotoxic T cell

secretes proteins that disrupt the membranes of target cells and trigger apoptosis

neutralization

antibodies bind to viral surface proteins preventing infection of a host cell

opsonization

antibodies bind to antigens on bacteria creating a target for macrophages or neutrophils, triggering phagocytosis

IgD

Membrane bound, mainly on the surface of mature, naive B cells, and in very small amounts as a secreted antibody in blood serum and mucosal secretions

IgM

First soluble class produced, predominantly in the blood and lymph fluid

IgG

Second soluble class; most abundant, blood circulation, extracellular fluid, and all other body fluids, placenta

IgA

Remaining soluble classes, in body secretion such á tears, saliva, and breast milk

IgE

Remaining soluble classes, triggering allergic reaction by binding to Fc receptor on mast cell and basophil