Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Endomembrane system wikipedia , lookup
Tissue engineering wikipedia , lookup
Extracellular matrix wikipedia , lookup
Cell growth wikipedia , lookup
Signal transduction wikipedia , lookup
Cytokinesis wikipedia , lookup
Cell encapsulation wikipedia , lookup
Cell culture wikipedia , lookup
Organ-on-a-chip wikipedia , lookup
Theoretical immunology/Microbiology Dept./Vet.Med. 2015---2016. Assist.Prof.Dr.Ikram Abbas Aboud Al-Samarraae B-Cell maturation, Activation, Differentiation and Humoral immune response:- Acquired immunity has two branches called Humoral Immunity (HI) and Cell Mediated Immunity (CMI). Its need another cell (Antigen Presenting Cell , APC) to present the antigen in a suitable form to cell . B-lymphocytes directly bind to antigen through their surface immunoglobulin receptor (B cell act as APC to help T cell ) . Upon antigen binding the B cell activated and divided repeatedly to produce plasma cells and memory cells . B – Lymphocyte Structure and Characteristics : Lymphocyte are small round cells ranging from 7 – 15 µm in diameter. The surface of some Lymphocytes are seen to be smooth , where as others are covered by many small projections . B cell originated in the bone marrow , but maturation in the payers patches . They are found in the cortex of lymph nodes , payers patches and spleen (in the marginal zone of the splenic white pulp . B – Lymphocyte Activation :The mature B – Lymphocytes released from bone marrow are in arresting state and they don’t secrete Abs .The resting B cell which don’t contact the antigen die within few days, whereas , arresting B cells , which binds to the antigen through the B cells surface immunoglobulins becomes activated . The activated B cells produces plasma cells & memory B cells .The activation of B cells requires two signals & cytokines from T cells:1-The first signal is provided by the binding of Ag to surface immunoglobulins on B cells surface. 2-Cell to cell contact between B cell & T helper cell provides the second signal required for B cell activation. The cytokines secreted by T helper cell bind to their respective receptors on B cell & help in proliferation & differentiation of B cells.The initial antibodies secreted by plasma cells in response to antigen always belong to IgM class . Memory B Lymphocytes:The memory B cells don’t secrete antibodies immediately .They remain in arresting state for many months to years .The memory B cells in the lymph 1 nodes are waiting for the contact with their specific antigens, upon contact with a specific antigen the memory B cell becomes activated & then divides to produce plasma cells & memory B cells. 2 3 Inhibition of B cell activation:Plasma cells die shortly, they have a life span of few days only and the Abs production is stopped .There is a negative feedback mechanisms that regulate the Abs production. The inhibition of B cell activation is probably mediated by the binding of Ag Abs complex to the B cell .The Ag combines with surface immunoglobulins that may interferring with the signaling mechanism inside the B cell, leading the suppression of B cell activation & finally new plasma cells production & Abs secretion don’t occur . The level of Abs induced against an Ag decreases. Antibodies- Mediated (Humoral) Immunity:When an individual encounters an antigen for the first time . antibodies to that antigen is detectable in the serum within days or weeks depending on the nature , dose of the antigen and the route of administration ( e.g . Oral , parenternal ) . The serum Abs concentration continues to rise for several weeks & then declines; it may drop to very low levels.The first Abs formed are IgM , followed by IgG , IgA or both .IgM tend to declines sooner than IgG levels. The Secondary Immune Response:In the event of a second encounter with the same Ag (or closely cross- reacting one) months or years after the primary response, the Abs response is more rapid & rise to higher levels than during the primary response .In the secondary 4 response the amount of IgM, produce in qualitatively similar to that produced after the first contact with Ag .However, much more , such Abs tends to bind Ag more firmly (to have higher affinity) and thus to dissociate less easily. 5 6