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Pathology
(Hypersensitivity Reaction)
By
Dr M. Dilawar Khan
Prof. & HOD Pathology
Azra Naheed Medical College, Lahore
Introduction
. Exogenous Ags ( Dust, pollens,
foods, drugs, Microbes, chemicals)
. Immune response due to Ag & Ab
interaction
. Examples ( Skin rash, Asthma, SLE,
Hemolytic anemia, Transplant
rejection)
Type-1 ( Anaphylactic type)
. Rapidly developing reaction
. Exposure of host to Ag already sensitized
. Reaction mediated by IgE production
. Ag & Ab complex attach to Mast cells & Basophils
.Release of histamine, ECF-A, proteases,
leukotrienes, prostagelandins
. Examples : Hey fever, Asthma, Anaphylaxis
Type II (Cytotoxic type)
. Mediated by Ab directed to Ag on the
cells/tissue components
. Complement activation by Ag /Ab complex
e.g. Transfusion reaction
. Effects of anti receptors Antibodies
e.g. Myasthenia gravis
.Ab dependent cell mediated cytotoxicity
e.g. Graft rejection
Type III (Immune Complex Disease
. Ag/Ab complex causes tissue damage
. Exogenous Ags (Streptococci, Actinomycetes,
Quinidine, Horse serum)
. Endogenous Ags (Nuclear, Ig, Tumors)
. Diseases (Serum sickness, SLE, Glomerulonephrits)
Type IV (Cell Mediated Type)
.Initiated by sensitized T lymphocytes
.Principal pattern for intracellular microbes
.Tuberculin reaction (Erythema , Induration)
.Memory T lymphocytes circulate for years
. Lymphokines recruit inflammatory cells
.Generation of cytotoxic T lymphocytes
Transplant Rejection
. Surgical expertise for transplant of Skin,
Kidney, Heart, Lung, Liver, Marrow
. Recognition of graft tissue as foreign
.T lymphocytes mediated reactions
.Antibody mediated reactions
.Graft Verses Host Disease(GVHD)
Autoimmune Diseases
. Reactions against self antigens
. Tissue damage break down products
.loss of self tolerance
.Single organ (Hashimoto’s Thyroidites)
.More organs (Good pasture’s Syndrome)
.Generalized (SLE, Rheumatoid Arthritis)
Immunologic Deficiency State
. Experiments of nature to document
immune system
. Primary (Inherited, Non specific, Cellular,
Humoral) e.g. Thymic Hypoplasia
.Acquired Immune Deficiency Syndrome
Questions
&
Answers