TEAS® Science Study Guide
Immune System
The immune system defends the body against pathogens: bacteria, viruses, fungi, and parasites.
Three lines of defense
- Physical and chemical barriers — Skin, mucous membranes, stomach acid, tears. Nonspecific; they block everything.
- Innate (nonspecific) immunity — White blood cells that attack any invader, plus inflammation and fever. Fast, but not targeted.
- Adaptive (specific) immunity — Lymphocytes that target one specific pathogen and remember it.
Adaptive immunity: two cell types
- B cells — Produce antibodies, proteins that bind to a specific antigen and mark it for destruction.
- T cells — Directly attack infected cells. Helper T cells coordinate the response.
Antigen vs. antibody — an antigen is the foreign marker on a pathogen. An antibody is what your body makes to match it. Students mix these up constantly.
Immunity and vaccines
Once you’ve fought a pathogen, memory cells remain, so the second exposure produces a faster, stronger response. Vaccines exploit this by introducing a harmless form of the antigen, creating memory without the illness.
Terms to know
- Pathogen — A disease-causing organism.
- Antigen — A foreign substance that triggers an immune response.
- Antibody — A protein made by B cells that binds a specific antigen.
- Lymphocyte — A white blood cell (B cell or T cell) in adaptive immunity.
What the TEAS asks most
- Which cells make antibodies? B cells.
- Antigen or antibody — which does your body produce? Antibody.
- What makes adaptive immunity different from innate? It’s specific, and it has memory.
- How do vaccines work? They create memory cells without causing disease.