In the initial stage of some diseases, infiltration by T lymphocytes may induce inflammation and tissue damage, leading to alterations in self antigens and production of autoantibodies. In other diseases, only the production of autoantibodies is noted with tissue damage. These autoantibodies attack cell sur face antigens or membrane receptors or combine with antigen to form immune complexes that are deposited in tissue, subsequently causing complement activation and inflammation.

An immune response requires presentation of a foreign anti gen by an antigen-presenting cell (APC) and another signal from the appropriate major histocompatibility complex (MHC) molecule on the host’s cells. Both are needed for an immune response. Tolerance is the lack of immune response to self anti gens and is initiated during fetal development (central tolerance) by the elimination of cells with the potential to react strongly with self antigens. Peripheral tolerance is a process involving mature lymphocytes and occurs in the circulation. Central tolerance develops in the thymus during fetal life. Self antigens are presented by dendritic cells to self-reactive T cells that are responsible for positive and negative selection of specific lymphocytes. The ultimate goal is to remove T lymphocytes that respond strongly to self antigens. As genes rearrange and code for antigen receptors, the T cell receptors (TCRs) produced may or may not be specific for the MHC expressed on that individual’s cells. Positive selection cells that have TCRs capable of responding with self antigens (low-level MHC affinity) are selected for continued growth.

Self-recognition (tolerance) is induced by at least two mechanisms involving contact between antigen and immunocompetent cells:

 • Elimination of the small clone of immunocompetent cells programmed to react with the antigen (Burnet’s clonal selection theory)

 • Induction of unresponsiveness in the immunocompetent cells through excessive antigen binding to them and triggering of a suppressor mechanism

 The normal immune response is modulated by antigen specific and antigen-nonspecific suppressor cell activity.

اخر الاخبار

اخبار العتبة العباسية المقدسة

العتبة العباسية المقدسة تنظّم محاضرة توعوية لطالبات كلية الأسوة للبنات في باكستان

الهيأة العليا لإحياء التراث تقيم دورة متخصّصة عن الفقه الكلامي

قسم التطوير يشرع بمقابلة المتقدمين للانضمام إلى أكاديمية التطوير الإداري

قسم الشؤون الفكرية يعلن انضمام جامعة كربلاء إلى المستودع الرقمي العراقي للأطاريح

المزيد

الآخبار الصحية

اختراع صيني.. لاصق يصلح كسور العظام خلال دقائق

اكتشاف حلقات عملاقة من الحمض النووي.. تقلل خطر السرطان

آباء أميركيون يطالبون بتنظيم روبوتات الدردشة لحماية الأطفال ؟

4 إشارات من القلب لا يجب تجاهلها أبدا

المزيد

الآخبار التكنلوجية

"تحليل المحادثات" يكشف كيف يستخدم الناس تشات جي بي تي

الدخان يكشف المستور.. التحنيط بدأ خارج مصر

مشهد مدهش للأرض من الفضاء.. جمجمة بيولوجية بعينين محدّقتين!

أول قطار يعمل بالهيدروجين في أميركا يدخل الخدمة رسميًا

المزيد

مواضيع ذات صلة

Hypersensitivity Reactions

Humoral/Antibody-Mediated Immune Response

Cell-Mediated Immune Response

Helper T Cells (Activation AND Differentiation)

Type III (Immune Complex) Reactions

Influenza virus immunology

Type II Antibody-Dependent, Complement-Mediated Cytotoxic Reactions

Immunologic Manifestations of Rubella infection

Antigen presentation

Cytokines

Structure of MHC Molecule

MHC Genes and Their Products