study guide 3

1. 3 lines of defense 1st line

physical/chemical barriers (skin, mucous, microbiota). 2nd line: innate immunity (phagocytes, inflammation, complement, fever). 3rd line: adaptive immunity (T/B cells, antibodies, memory).

2. Blood cell types & origin

All blood cells come from bone marrow. RBCs = O2 transport. Platelets = clotting. WBCs = immune defense: neutrophils (phagocytes), eosinophils (parasites), basophils/mast cells (histamine), macrophages (phagocytosis), lymphocytes (B/T/NK cells).

3. Cell communication

Immune cells communicate via cytokines, chemokines, receptors to coordinate response.

4. Sensor system signals

PAMPs detect microbes (LPS, flagellin). DAMPs detect host cell damage. Both trigger immune activation.

5. Phagocytosis

Engulf & digest microbes. Done by neutrophils, macrophages, dendritic cells.

6. Inflammation

Response to infection/injury. Steps: vasodilation → permeability ↑ → phagocytes recruited → tissue repair. Purpose: contain infection & heal.

7. Complement & MAC Complement

opsonizes pathogens, triggers inflammation, forms MAC to lyse bacteria.

8. Interferons

Antiviral proteins that warn nearby cells after viral infection.

9. Why adaptive immunity is specific

Uses specific antigen receptors. Main cells: B cells & T cells.

10. Humoral immunity

B cells make antibodies → attack extracellular microbes.

11. Cellular immunity

T cells kill infected or abnormal cells directly.

12. Lymphoid system

Produces & activates immune cells. Primary: bone marrow, thymus. Secondary: lymph nodes, spleen, MALT, tonsils.

13. Antigen Trigger immune response. Proteins are the best antigens.

14. Antibody binding

Antibodies bind specific antigen epitopes via variable region.

15. Antibody classes

IgG = most abundant, long-term. IgM = first made. IgA = mucosal. IgE = allergies/parasites. IgD = B cell receptor.

16. B cell activation

B cell binds antigen + T cell help → plasma cells & memory B cells.

17. T cell activation

Recognize antigen on MHC → helper T cells (activate others) & cytotoxic T cells (kill infected cells) + memory T cells.

18. Primary vs secondary response

Primary = slow, symptoms. Secondary = fast & strong due to memory, fewer symptoms.

19. Natural killer cells

Kill virus-infected & cancer cells without prior exposure.

20. Adaptive immunity summary

Antigen recognized → helper T cells activate → B cells make antibodies → cytotoxic T cells kill infected cells → memory cells formed.

21. Microbe interaction & escape

Entry → adhesion → invasion → immune evasion (capsules, antigen changes, toxins) → damage.

22. Normal flora

Helpful microbes on skin, GI, respiratory, urogenital systems. Built through birth, environment, diet.

23. Infection vs disease Infection

= microbe multiplies. Disease = symptoms. Signs = measurable (fever). Symptoms = felt (pain).

24. Pathogenicity & stages

Ability to cause disease. Stages: incubation → prodromal → illness → decline → recovery.

25. Infection establishment

Entry → adhesion → colonization → invasion → damage.

26. Avoid host defenses & cause damage

Capsules, hide inside cells, toxin production, immune suppression. Damage from toxins & immune response.

27. Asymptomatic infections

Yes — infection without symptoms if immune control is strong.

28. How microbes exit

Droplets, feces, urine, blood, skin, sexual fluids → transmission to new hosts.

29. Epidemiology

Study of disease distribution, causes, and spread in populations.

30. Communicable vs non-communicable

Communicable spreads between people. Non-communicable does not (tetanus, food poisoning).

31. Epidemiologists & disease rates

Track incidence, prevalence, mortality, attack rates to measure spread & severity.

32. Chain of infection

Reservoir → portal of exit → transmission → portal of entry → susceptible host.

33. Reservoirs

Where pathogen lives: humans, animals, soil, water.

34. Transmission modes

Direct contact, droplets, airborne, vectors, contaminated food/water, fomites.

35. Factors influencing epidemiology

Pathogen traits, host immunity, population density, environment, sanitation, behavior.