Mechanism of Type I: Sensitization steps and Hypersensitivity
Sensitization: --> Dendritic Cells bind to a pollen (antigen) - present the antigen to T helper 2 cell with MHC2. - T cell then clone itself to produce MEMORY T helper 2 cell, and at the same time call for help from B cell. - B cell then clone itself for MEMORY B cell at the same time makes PLASMA cells to produce adjacent IgE antibodies. (later will bind to mast cells or basophils in order to recognize antigen)
Hypersensitivity --> When pollen antigen is bind to adjacent antibodies of mast cell or basophil, degranualation occur, where histamine and other mediators are released.
Allergens associated with FOOD and POLLEN
AKA. Anaphylatic shock
*associate with venoms --- MECHANISM?
mediators --- cause peripheral blood vessels to expand = sudden drop in blood pressure --- SHOCK
*Treatment --- Epinepherine Pen to contrict blood vessels.
*prevention --- Desensitization = increase IgG instead of IgE. Repeatedly expose to increasing dosage of denatured antigen. effective with animal venoms.
Type II. CYTOTOXIC REACTION
*Antibodies IgG & IgM
*Complement gets activated as a result of anitbodies binding to the antigen. ---causing cell lysis and damge.
*EX--- Immune complex, but no cytotoxic,
Most common --- blood transfusion, HEMOLYTIC disease = Rh - mother and Rh+ fetus
---> can be prevented by determining the patient's blood type as well as Rh
*5 - 10 hrs symptoms occur
Mother is Rh -, when carrying a baby that is Rh +, when breaks in placenta, the antigen from Rh + baby enters the mother's body, making her body produce Anti Rh anitbodies. When the mother is pregnant the second time, the baby with a positive Rh will attract the anti Rh antibody from the mother and lead to attack of the fetus red blood cells.
*Prevent sensitization by administering the mother with Anthi Rh first,
TYPE III (immune complex) hypersensitivity
antigen binds to antibodies don't get destroyed, but rather attach to host tissue, causing an intense immune response = inflammation of tissue. Tissue destruction often occur
*Arthus Reaction --- Local, injection of antigen with a patient that has a large amount of IgG to antigen; EDEMA and HEMORRHAGING = DEAD tissue.
Type IV (Cell mediated) Hypersensitivity Reaction
*This reaction only deals with T helper cells only. NO ANTIBODY
*takes about 12 hrs+
*EX Poison IVY - dermatitis; TB, indication.
*In this reaction, Sensitized T helper 1 bind to PRESENTING cell, secrete Cytokines to attract Macrophages and initial inflammation action tissue damage.
Systemic Lupus Erythematosus
*IgG, IgM, IgA antibodies are produced against patient's DNA --- during normal cellular death process. immune complexes deposited in skin, joints, CNS. etc.
*occur more frequently in women, butterfly rash on the face.