clinmedimmunity

• Cellular Response (lymphocytes - direct response, detect foreign cell/material)
• Humoral Response (antibodies circulate in the blood)

• B - Cells - (derived from bone marrow, matures in Butt?)
• T- Cells - (originate from the bone marrow, matures in the Thymus)

B-cells react when antibodies come into contact w/ antigen. B-cells differentiate into plasma cells. Plasma cells then produce antibodies specific for the antigen stimuli of original B-cell.

• 1. pre-B cell: contain receptors on plasma membrane but no surface immunoglobulin (NO IDENTITY)
• 2. early-B cell: immature... recognized by surface IgM and later IgD
• 3. isotype switching: expression on the surface of other immunoflobulins - IgG, IgA, IgE
• 4. mature B-cells: constitute 10-20% of pperipheral lymphocytes awaiting activation by foreign Antigen (sensitization) immunogl. isotypes IgG, IgM, IgA
• 5. Plasma Cells: make antibodies, requires exposure to additional T-cell products but sometimes cytomegalovirus activation can be direct

During activation B-cells dividing under modulation of T-cells, most of the new B-cells become a "selected clone" of the plasma cells and pump out specific antibodies.

When the immune system "wins" the plasma cell dies, but plenty of the B-cell clones survive and have memory --> future presence of that same antigen will trigger greater antibody response

• T cells DO NOT USE ANTIBODIES nor have them on their surfaces.
• But specificity of the antigen recognition is guaranteed by the receptor presented on the plasma membrane.
• Important for protection against Tumors, intracellular bacteria, viruses, parasites, and reactions to transplant
• Centerpiece of immune system

• 1. some are DIRECTLY CYTOTOXIC
• 2. some participate in RELEASE of vaious CYTOTOXIC MEDIATORS
• 3. some are involved in STIMULATION of B-Lymphocytes

• CD4 - helper "commander"
• CD8 - Cytotoxic "soldier"
• CD3 - ???

they're categorized by expression of specific surface marker proteins --> CD - cluster designations

• Early cortical T-cells (least mature thymocytes, make up 10% of all T-lymphocytes)
• Late cortical T-cells (thymocytes that account for 80% of thymic populsion
• Medullary T-cells (CD-4 helper 50% and CD-8 Cytotoxic 50%, located in medulla of thymus)
• Peripheral T-cells (T-lymphocytes released to the blood with 65% (Cd-4 helpers) and 35% (Cd-8 cytotoxic)

• 10-15% of Blood lymphocytes
• NK's are the First line of defense vs neoplastic tumors and virus infected cells since they can lyse them without prior sensitization
• special type of Large lymphocytes (formerly known as non-t/-non-B or NULL cells)

• They are immune responses to antigiens that can cause tissue damaging reactions
• Resultant tissue lesions --> Hypersensitivity disease
• They're classified on the basis of the mechanism mediating the disease

• Mediated by IgE antibody sensitization
• immune response release vasoactive mediators from MAST cells or Basophils that affect vascular permeability and smooth muscle
• "ALLERGY reaction" --> activation of MAST cells, Basophils, releasing:
• 1. Histamine as primary mediator
• 2. Prostoglandins, lukotrienes as secondary mediators
• Can be 1. LOCAL - (itching swelling sneezing, eyes and nasal)
• 2. GENERALIZED - (bronchoconstriction, cirulatory collapse, Anaphylactic shock/syndrome)

• IgG and IgM Mediated
• Classes of antibody participate in indirect cytotoxicity
• Antibodies binding to an antigen on surface of cells --> induce activation of COMPLEMENT which leads to target cell destruction by:
• 1. DIRECT LYSIS (membrane attack complex C5-9)
• 2. OPSONIZATION (enhancing phagocytosis (C3b)
• Examples: (many autoimmune disease eg Hemolytic anemia, Graves disease, Myasthenia Gravis)

• Antigen - Antibody Complex disease
• Mediated IgM, IgG, IgA complexes formed in circulation and deposted in different tissues -->
• presence acitivates complements, Chemotaxis (of neutrophils --> trigger acute inflam rxn impairing tissue fx
• examples: SLE or Lupus

• cell-mediated immmune response (NO ANTIBODIES)
• antigens are processed bt macrophages and presented to cytotoxic T-cells --> their activation relaease of mediators
• --> destroying plasma membrane and target cells
• examples: Sjorgen syndrome