SOME KEY POINTS

T-cell B-cell• From thymus Bursa of fabricius• 80% of circulating 20% of circulating lymphs in blood  • Long lived • T-Cell receptors Ig receptors on its surface• T-cells "see" antigen as peptides ONLY in association with host surface MHC (Major histocomptability) molecules • There are three classes of MHC molecule1) MHC class I , which primarily present intracellular antigens. 2) MHC class II , which primarily present extracellular antigens. 3) MHC class III: components of complement system (C2, C4, Bf) code for MHC• CD8+ Tc cells can only recognize antigen in association with MHC I. • CD4+ Th cells can only bind antigen in association with MHC II. 

MACROPHAGES: • In liver, are k/a kupffer cells• In spleen, littoral cells• In skin, langerhans cells• In lymph node, dendritic cells 

Major histocompatibility complex (MHC) / Human leukocyte antigen ( HLA) • Gene is present on the short arm of chromosome no. 6 • MHC class I Ags • are expressed on every nucleated cell of the body• HLA-A, HLA-B, HLA-C• MHC class II Ag are expressed only on cells involved in the immune response• Lymphocytes • Macrophages• Endothelial cells• MHC class III region• Encodes for complement components (e.g., C2, C4, factor B) and some encode cytokines (e.g., TNF-α) . 

Diseases asso with HLA types: • Ankylosis spondylitis– HLA-B27• Post gonococcal arthritis—HLA- B27• Rheumatoid arthritis---HLA-DR4• Primary Sjogren Syndrome– HLA-DR3• Hemochromatosis---HLA-A3 

Hypersensitivity  refers to undesirable (damaging, discomfort-producing and sometimes fatal) reactions produced by the normal immune system. Hypersensitivity reactions require a pre-sensitized (immune) state of the host. • Type I: anaphylactic rxn• Type II: cytotoxic type• Type III: Immune complex disease• Type IV: Cell mediated/ delayed HST 

Comparison of Different Types of hypersensitivity characteristics type-I(anaphylactic type-II(cytotoxic type-III(immune complex type-IV(delayed type)antibody IgE IgG, IgM IgG, IgM noneantigen Exogeneous Cell surface Soluble tissues & organsRespnse time 15-30 min minutes-hours 3-8 hrs 48-72 hoursappearance Wheal & flare lysis and necrosis erythema and edema,necrosis erythema and indurationhistology basophils and eosinophil antibody and complement complement and neutrophils monocytes and lymphocytestransferred with Antibody Antibody Antibody T-cellexamples allergic asthma, hay fever Erythroblastosis fetalis, Goodpasture's nephritis SLE, farmer's lung disease  tuberculin test, poison ivy, granuloma

Transplant rejection occurs when a transplanted organ or tissue fails to be accepted by the body of the transplant recipient. Types of rejection:1. Hyperacute rejection: Hyperacute rejection is a complement-mediated response in recipients with pre-existing antibodies to the donor (for example, ABO blood type antibodies). Hyperacute rejection occurs within. This is a particular risk in kidney transplantsHyperacute rejection is the likely outcome of xenotransplanted organs.2. Acute rejection: Acute rejection usually begins one week after transplantation (as opposed to hyperacute rejection, which is immediate). The risk of acute rejection is highest in the first three months after transplantation. It is caused by mismatched HLA antigens, which are present on all cells of the body. Tissues such as the kidney or the liver which are highly vascularized (rich in blood vessels), are often the earliest victims of acute rejection3. Chronic rejection: The term "chronic rejection" was initially a term used to describe a long-term loss of function in transplanted organs, associated with fibrosis of the internal blood vessels of the transplanted tissue It can be caused by a member of the Minor Histocompatibility Complex such as the H-Y gene of the male Y chromosome.Rejection mechanisms: Rejection is an adaptive immune response and is mediated through both T cell mediated and humoral immune (antibodies) mechanisms. 

Systemic Lupus Erythematosus Eleven Criteria established by the American Rheumatism Association • malar (over the cheeks of the face) "butterfly" rash • discoid skin rash: patchy redness that can cause scarring • photosensitivity: skin rash in reaction to sunlight exposure • mucus membrane ulcers: ulcers of the lining of the mouth, nose or throat • arthritis: 2 or more swollen, tender joints of the extremities • pleuritis/pericarditis: inflammation of the lining tissue around the heart or lungs, usually associated with chest pain with breathing • kidney abnormalities: abnormal amounts of urine protein or clumps of cellular elements called casts • brain irritation: manifested by seizures (convulsions) and/or psychosis• blood count abnormalities: low counts of white or red blood cells, or platelets • immunologic disorder: abnormal immune tests include anti-DNA or anti-Sm (Smith) antibodies, falsely positive blood test for syphilis, anticardiolipin antibodies, lupus anticoagulant, or positive LE prep test • antinuclear antibody: positive ANA antibody testing 

Sjögren's syndrome • autoimmune disorder in which immune cells attack and destroy the exocrine glands that produce tears and saliva • Patients with Sjögren's syndrome have a higher rate of non-Hodgkin lymphoma • The most common lymphomas are salivary extranodal marginal zone B cell lymphomas

(MALT lymphomas in the salivary glands) and diffuse large B-cell lymphoma

Amyloidosis• amyloidosis refers to a variety of conditions in which amyloid proteins are abnormally deposited in organs and/or tissues, causing disease • at least 15 biologically distinct forms of amyloid • .Amyloid type Description• ALamyloid light chain Contains immunoglobulin light-chain (λ,κ) derived from plasma cells• AAamyloid associated Non-immunoglobulin protein made in the liver• Aββ amyloid Found in Alzheimer disease brain lesions• ATTRTransthyretin A mutant form of a normal serum protein that is deposited in the genetically determined familial amyloid polyneuropathies. • TTR is also deposited in the heart in senile systemic amyloidosis.• Aβ2 m β2 microglobulin Not to be confused with Aβ, β2m is a normal serum protein, part of major Histocompatability complex (MHC) Class 1molecules. Can occur in long term haemodialysis.• PrP Prion related protein In Prion diseases, misfolded prion proteins deposit in tissues and resemble amyloid proteins.

Classification of amyloidosis• Primary (disordered immune cell function) :multiple myeloma and other immunocyte dyscrasias. • Secondary (reactive) :as a complication of some other chronic inflammatory or tissue destructive diseaseAcquired immune deficiency syndrome or acquired immunodeficiency syndrome (AIDS or Aids) is a set of symptoms and infections resulting from the damage to the human immune system caused by the human immunodeficiency virus (HIV

Major Ag of HIV • Envelope Ag: gp120, gp 41• Shell Ag p18 (nucleocapsid protein)• Core Ag : p24, p15, p55• Polymerase Ag: p31, p51, p66