Immune

IL-1

Fever, acute inflammation; activates endothelium to express adhesion molecules; secreted by macrophages

IL-2

Stimulates growth of helper, cytotoxic, and regulatory T cells; secreted by Th cells

IL-3

Supports growth and differentiation of bone marrow stem cells; similar to GM-CSF

IL-4

Induces Th2 differentiation; promotes B cell growth; class switching to IgE and IgG

IL-5

Promotes eosinophil activation and growth; class switching to IgA

IL-6

Induces fever and stimulates acute-phase protein production in liver

IL-8

Major chemotactic factor for neutrophils; recruits them to infection sites

IL-10

Anti-inflammatory cytokine; inhibits Th1 responses; secreted by Tregs and Th2 cells

IL-12

Stimulates differentiation of Th1 cells; activates NK cells; secreted by dendritic cells and macrophages

IL-17

Secreted by Th17 cells; induces neutrophilic inflammation and antimicrobial peptides

IL-23

Maintains and stabilizes Th17 cell responses; works with IL-6 and TGF-β

IFN-α and IFN-β

Antiviral cytokines; increase MHC I expression and activate NK cells

IFN-γ

Activates macrophages; increases MHC II expression; secreted by Th1 and NK cells

TNF-α

Inflammatory cytokine; causes fever, septic shock, and increased vascular permeability

TGF-β

Anti-inflammatory cytokine; promotes tissue repair and Treg differentiation

C3a

Complement fragment that causes mast cell degranulation and inflammation

C3b

Opsonin; tags pathogens for phagocytosis

C5a

Potent chemoattractant for neutrophils; also causes mast cell degranulation

C5b-C9 (MAC)

Form membrane attack complex; punch holes in pathogen membranes

CD4

Coreceptor on helper T cells that binds MHC II

CD8

Coreceptor on cytotoxic T cells that binds MHC I

CD28

T cell costimulatory molecule that binds B7 on APCs

CD40L

Expressed on T cells; binds CD40 on B cells and macrophages to activate them

CD18

Integrin involved in leukocyte adhesion; deficiency causes LAD (Leukocyte Adhesion Deficiency)

Fc receptor

Binds Fc portion of antibodies on phagocytes or mast cells; enables antibody-mediated functions

MHC I

Present on all nucleated cells; presents endogenous peptides to CD8+ T cells

MHC II

Present on APCs; presents exogenous antigens to CD4+ T cells

TCR

T cell receptor; recognizes antigen bound to MHC

BCR

Membrane-bound immunoglobulin on B cells; recognizes specific antigen

TLRs (Toll-like receptors)

Recognize pathogen-associated molecular patterns (PAMPs); activate innate immune response

G-CSF

Stimulates production of neutrophils from bone marrow

GM-CSF

Stimulates granulocyte and macrophage production

M-CSF

Stimulates differentiation of monocytes into macrophages