Types of Immunity n Innate vs Acquired n

Types of Immunity n Innate vs. Acquired n Active vs. Passive n Natural vs. Artificial 1

Antigens n Epitopes n Haptens 2

Antibodies and Cells n B lymphocytes n T lymphocytes – 4 sub-types n Natural Killer cells 3

Nature of the Immune system n Humoral Immunity n Cell-mediated Immunity – Cell lysis, apoptosis – Foreign eukaryotic cells 4

General Immune System Properties n Self versus Non-self Recognition – Maturation leads to ________ – Defects = ____________ n Specificity – Random gene rearrangements create potential binding sites for antigens – Some cross-reactivity 5

General Immune System Properties n Diversity – Over 1 billion antigen binding sites are possible n Memory – Sub-populations of stimulated lymphocytes remain in lymph nodes to provide a faster, larger response on second antigen encounter – Basis of “Immunity” or the anamnestic (secondary) response 6

Nature of the Immune system Clonal stimulation n n n B lymphocyte binds ____ Bound Ag is engulfed and fragmented within the B cell Ag fragments + ______________ (MHC II) proteins together = presented or “processed” antigen Triggers _________ (IL-2) production from T cells This stimulates B cells further and creates memory cells Known as ____________, usually proteins 7

Antibody Anatomy n Heavy/Light Chains n Variable/ Constant Regions n Antigen Binding Site n Disulfide Bridges 8

Immunoglobulin Classes n Ig G n Ig. A n Ig M n Ig E (reagin) n Ig D 9

Immune Memory n Primary Response – – n Ig. M initially Ig. G detectible in 2 -3 weeks Levels may drop after initial exposure Memory cells persist Secondary Response – Much larger response of Ig. G – Protection against invading microbes and toxins 10

Antigen Types n T-independent – No helper T cells – No memory cells are created – Only Ig. M – Carbohydrate Ag, often capsular on bacteria n T-dependent – – Needs helper T cells Creates memory B cells Ig. M and Ig. G Protein Ag 11

Effects of Ag/Ab Reactions n Agglutination – Reduction of target count n Neutralization – Viral and bacterial binding sites for host cell attachment are blocked n Complement-mediated effects – FC fragment (Constant region) activates complement • Cytolysis • Opsonization • Increased inflammation 12

Monoclonal Antibodies n MAbs – Multiple myeloma cells + normal lymphocytes – Hybrid cells are • Immortal in large-scale cell culture • Specific Ab producers – Uses • Diagnostic – Pregnancy – Strep. Throat – Chlamydia STD • Anticancer – Chemo agents may be attached • Anti-tissue rejection – Allergies to mouse proteins are a challenge • Humanized Mabs 13

Cell Mediated Immunity n Activation – Processed antigens presented alongside MHC proteins • TH cells are activated by Ag + MHC II, antigen presenting dendritic cells, B cells or macrophages • TC cells are activated by Ag + MHC I , usually infected cells with intracellular virus or bacteria, transformed cells or transplant cells n Memory T cells can form 14

T Cell Types n Helper T cells (TH) release lymphokines – IL-2 • stimulates Ab production • Activates TC cells – Gamma IFN • Co-ordinates inflammatory response • Antiviral and anti-tumor n Delayed Hypersensitivity T cell (TD) – TD cells release lymphokines that control macrophage movement/inflammation 15

T Cell Types (cont. ) n Cytotoxic T cells (TC) – Produce Perforin proteins – Lyse virally infected cells n Natural Killer cells – Produce Perforin proteins – Lyse tumor and bacterially infected cells – Activated by lack of MHC proteins on cell membranes, no clonal stimulation 16

Mucosal Immune System Mostly Ig. A production n 400 square meters (4500 square feet!) n Gut, GUT, Resp. tract n 17

Factors Modifying the Immune System n Disorders/Injuries n – Genetic tendencies – Genetic diseases n Environment – Seasonal – Pollution – Rediation Lifestyle – Diet – Exercise – Addictions n Age – Middle life most healthy 18

Immunization n Active n Passive – Ag administration – Ab administration – Toxoid or microbial structural molecule – Temporary, protection declines – Live vaccines provide longer protection – Will affect the course of a disease – Route of administration affects protection level – Allergic reactions are commonest drawback 19

Future Considerations n Criteria for new vaccines 20

Immunity to Specific Pathogens n n Bacteria Viruses n Fungi n Protozoa/Helminths 21