Effector Cells and Molecules

Epithelial cells

Form physical barrier; secrete antimicrobial peptides (like defensins) and cytokines — Innate effector cell

Phagocytes

Ingest and destroy invaders — Innate effector cell

Neutrophils

First responders; phagocytose and kill microbes; form NETs (neutrophil extracellular traps) — Innate effector cell

Dendritic Cells (DC)

Capture antigens and present to T cells; bridge innate and adaptive immunity — Innate effector cell

Monocytes/Macrophages (Mo/Mph)

Phagocytose pathogens and dead cells; present antigens; release cytokines — Innate effector cell

Eosinophils

Kill parasites (especially worms); release toxic granules; involved in allergy — Innate effector cell

Basophils

Release histamine; involved in allergic reactions — Innate effector cell

Lymphocytes (Ly)

Adaptive responders; include B cells, Helper T cells (TH), and Cytotoxic T cells (CTLs) — Adaptive effector cell

B cells

Produce antibodies; can also present antigens — Adaptive effector cell

Helper T cells (TH)

Activate B cells, CTLs, and macrophages using cytokines — Adaptive effector cell

Cytotoxic T cells (CTLs)

Kill virus-infected cells — Adaptive effector cell

Natural Killer Cells (NK)

Kill virus-infected and tumor cells without needing specific antigens — Innate effector cell

Antimicrobial peptides and proteins

Direct; kill bacteria, fungi, some protozoa (e.g., lysozyme); disrupt membranes — Innate effector molecule

Complement

Direct; triggers proteolytic cascade; promotes inflammation and phagocytosis; forms pores in bacterial membranes leading to cell death — Innate effector molecule

Antibodies

Indirect; recognize and bind antigens; assist in complement activation and target pathogens for destruction — Adaptive effector molecule