Human Phys Chap 15

Immune System

Protects against infection

Isolate/remove non-microbial foreign substances

Destroy cancer cells

Innate Immune System

Non-specific, born with, Immediate response:

Barriers (mucus), phagocytes, NK cells, inflammation

Adaptive Immune System

Specific / Post-Vaccination / Trained

Slow response, strong memory:

B cells and T Cells

Leukocytes (WBC)

Neutrophils: Most, bacteria and some infected cells

Eosinophils: Parasites

Basophils: Allergic Reaction (Histamine)

Monocyte: On RBC, macrophages

Lymphocytes: B cells, T cells

Hematopoietic Stem Cell Origin

Lymphoid → Lymphocytes

Myeloid → others + RBC + Platelets

Innate Immunity 1

Complement: Proteins to bacteria = explode

PAMP = Pathogen, PRR = all cells (from Toll-Like Receptors)

Innate Immunity 2

Inflammation: tissue damage, destroy debris, prep repair

Bring phagocyte to invaded area:

Antibodies on pathogen → Detection → Mast cell release histamine → Dilation → taxied phagocyte → extraversion

Signs: Swelling, Pain, Heat, Redness

Innate Immunity 3

Chemotaxis: Bring cell to or from SOS signal

Cytokines: SOS signal

Extravasion: WBC - “Here’s Johnny!”

Fever: macrophage release endogenous pyrogen → increase temp

Innate Immunity 4

Interferons: Last-Ditch to save other cells

Viral cell → DNA, proteins, interferons

IF exits to healthy cell and blocks (protects), takes time

Innate Immunity 5

Classical: Antibodies “tag” pathogen (opsonization)

Alternative: Complement “tag” broad targets

• 1) Recognize - C1

• 2) Approach - C2, C3, C4

• 3) Attack - C5 to C9

Attacks via apoptosis (programmed death via proteins) or lyse (explode via overexpansion w/ H2O)

Adaptive Immunity 1

Responds by recognizing specific antigen (foreign molecule on surface)

Adaptive Immunity 2 (Lymphoid Organs)

Primary: site of maturation (B → Bone Marrow, T → thymus); two chances to recognize or death

Secondary: Encounter/activation (Lymph nodes/vessels, tonsils, spleen)

Adaptive Immunity 3 (Clonal Selection Theory)

Memory: specific lymphocyte for specific pathogen

Exposure = production of clones & memory cells

Adaptive Immunity 4

Antibody-mediated / Humoral Immunity:

• Produce antibodies by plasma cells

Cell-mediated:

• Produce activated T cells

(Attack unwanted & support other cells)

B Lymphocytes

Surface receptor binds to specific antigen

Differentiates into plasma (Fighter) & memory (Scientist) cells

• Plasma: Fires more antibodies

• Memory: Keeps antibodies for future

Immunoglobulin

IgG: Abundant Protector (Main form)

IgA: External Secretions (Breast Milk / Placenta)

IgE: First-Response (Allergic Symptoms / Largest)

IgM: Allergy / Parasite

IgD: B-cell Signal

T Lymphocytes

Cytotoxic (Killer) T Cells (DPS):

• Direct Killing, Virus/Cancer cells, CD8+ receptor

Helper T Cells (Scout):

• Comms w/ B Cells, modulates activities, CD4+ receptor

Suppressor T Cells (Support):

• Regulator, dampen response (Don’t kill all)

Antigen Presentation (T Cell can’t identify unless presented)

Macrophages, Dendritic Cells, B Cells

MHC I = Target cells (all nucleated cells)

MHC II = Antigen-Presenting Cells

APC Sequence (B cell)

Engulf Antigen → Load MHC → bind to T cell → Activate T cell → Tell B cell → Differentiate into Plasma & Memory

APC Sequence (T Cell)

→ IL-2 Cytokine → Cytotoxic detects → Cytotoxic clones → Cytotoxic Kills

Cytotoxic Function

Upon contact, secretes perforins and granzymes, lysing target cell

Active Immunity (Initial)

Response to microbe exposure

Primary forms effector and memory cells

If pathogen is back, larger and faster response (Secondary)

Passive Immunity (Borrowed)

Antibody transfer / Immediate protection / Resistance

Ex: mother to fetus during pregnancy

Autoimmune (inappropriate)

Immune System tries to attack own body (Loss of tolerance)

B cells produce AB that bind to self-antigens

Cytotoxic attacks those self-antigens

Ex: Lupus, Type I diabetes

Immunodeficiency

Genetic or environmental

HIV: Infects and kills Helper (no comms, reduced function)

AIDS: Susceptible to infection or cancer

Hypersensitivity

Response to allergens; genetically predisposed individuals (mediated by IgE antibodies)

Surveillance

B/T cells | NK Cells

Tumor cells can evade by suppression

Natural Killer (NK) Cells

Like T cells; part of innate immunity

Kills w/o discrimination (malignant cells or virus-infected cells)

Aging and Stress

Cancer risk increases with age

Thymus function reduced; reduced cell-mediated function

Cortisol: suppresses immune system (in survival mode)

Malignancies (fast growth and spread)

Lymphomas: Malignant B cells

Leukemia: Non-functional WBC from Bone Marrow

Myeloma: Plasma cells (can’t build/release antibodies)