2nd try

Innate immunity

A built-in defense system you are born with; fast and general (skin, mucus, certain white blood cells, complement proteins).

Adaptive immunity

A defense that learns and remembers specific germs; uses B cells and T cells to make a targeted attack.

Dendritic cells

Scout cells that capture pieces of germs and show them to T cells to start the adaptive immune response.

Macrophages

“Big eaters” that swallow and digest germs; also present germ pieces to T cells.

Neutrophils

First-responder white blood cells that quickly attack and digest germs.

T cells

Main commanders and soldiers of adaptive immunity; include CD4 helper T cells (give orders) and CD8 killer T cells (destroy infected cells).

B cells

White blood cells that make antibodies; some become long-lasting memory cells.

Natural Killer (NK) cells

Cytotoxic cells that kill virus-infected or cancer cells without needing antibodies or T cell signals.

Cytokines

Chemical messengers released by immune cells to coordinate inflammation and defense.

Chemokines

A special type of cytokine that attracts immune cells to the site of infection (chemo-attractant).

Antibody (Immunoglobulin)

Y-shaped protein made by B cells that binds and tags germs for destruction.

IgM

The first antibody made during a new infection; good at forming clusters of germs.

IgG

The most common antibody; provides long-term protection and crosses the placenta to protect babies.

IgA

Antibody found in saliva, tears, and breast milk; protects surfaces like the gut and lungs.

IgD

Antibody that helps activate B cells; less understood.

IgE

Antibody involved in allergies and defense against parasites such as worms.

Pathogens

Microbes that cause disease: bacteria, viruses, fungi, parasites.

Benign tumor

Non-cancerous growth that does not spread.

Malignant tumor

Cancerous growth that can invade nearby tissues.

Metastatic tumor

Cancer that has spread to new parts of the body.

Pathogen-Associated Molecular Patterns (PAMPs)

Common molecular patterns on microbes recognized by immune sensors.

Damage-Associated Molecular Patterns (DAMPs)

Signals from injured or dying body cells that alert the immune system.

Toll-like receptors (TLR)

Surface sensors on immune cells that detect microbial patterns.

RIG-like receptors (RLR)

Inside-cell sensors that detect viral RNA.

NOD-like receptors (NLR)

Cytosolic sensors that detect bacterial cell wall pieces and trigger inflammation.

C-type lectin receptors

Surface receptors that recognize certain sugars on microbes.

Complement system

A group of blood proteins that mark microbes for destruction, cause inflammation, and punch holes in germ membranes.

Classical pathway

Complement pathway triggered when antibodies bind to a microbe.

Alternative pathway

Complement pathway triggered directly by microbes (part of innate immunity).

Lectin pathway

Complement pathway triggered when lectin proteins bind to sugars on microbes.

Opsonization

Coating of a microbe with proteins (like antibodies or C3b) to help phagocytes grab and eat it.

C3a and C5a

Complement fragments that cause inflammation and attract immune cells.

C3b and C5b

Complement fragments that attach to germs for opsonization or to form membrane attack complexes.

Regulatory T cells

T cells that prevent overreaction and keep the immune system from attacking the body’s own tissues.

M1 macrophages

Classical macrophages that kill microbes and trigger inflammation.

M2 macrophages

Alternative macrophages that help repair tissue and calm inflammation.

Pus

Thick fluid made of dead bacteria and dead white blood cells.

Hematopoiesis

The process of making new blood cells in the bone marrow.

Endocrine signaling

Chemical signals that travel through the bloodstream to distant cells.

Paracrine signaling

Chemical signals that act on nearby cells.

Autocrine signaling

Chemical signals that act on the same cell that released them.

Spleen

A lymph organ that filters blood, traps microbes, and helps launch immune responses.

Lymph nodes

Small immune hubs that filter lymph fluid and provide meeting places for immune cells.

High Endothelial Venules (HEV)

Special blood vessels that let immune cells enter lymph nodes.

Integrins

Proteins on white blood cells that help them stick to blood vessel walls and move into tissues during infection.

ICAM-1

Adhesion molecule on blood vessel cells that helps white blood cells attach.

VCAM-1

Adhesion molecule that helps white blood cells move from blood into tissues.

Interleukin-12 (IL-12)

Cytokine that helps Natural Killer (NK) cells mature and become active.

Type I Interferon (IFN-α/β)

Antiviral cytokines that block viral replication and warn nearby cells.

Interferon-gamma (IFN-γ)

Cytokine from NK cells and T cells that activates macrophages to kill microbes.