Cytokines antigen presentation

Figure 6.2 Subsets of T helper (CD4 ) lymphocytes are now recognized which synthesize different patterns of cytokines. Antigen presentation to lymphocytes by antigen-presenting cells (predominantly dendritic cells in the airways) results in clonal expansion of Th2 lymphocytes.

Parallel to orchestrating acute inflammatory processes by providing an optimal milieu of cytokines, mediators, and adhesion molecules in order to recruit and activate effector cells to the site of infection, dendritic cells also setve as professional antigen-presenting cells for cells of the adaptive immune system ( antigen presentation ... 

In the specialized environment of secondary lymphoid tissues such as lymph nodes or spleen, dendritic cells provide the requirements for naive T-lymphocytes to become activated and to proliferate. The professional antigen-presenting cells present peptides in MHC II, express costimulatory molecules, and release cytokines into the immunological synapse, which is formed by the antigen-presenting cell and the naive T-lymphocyte. Thus, cells of innate immunity initiate and facilitate the activation of naive lymphocytes, and it is easily conceivable that their cytokines and adhesion molecules will instruct the naive T-lymphocyte during activation and differentiation to T-effector cells. 

B cells also have impact on T-cell differentiation. B-cell antigen presentation plays an important role at promoting Th2 responses and pathophysiology during allergic disorders. It has been shown that B-cell -/- mice and in mice selectively deficient in MHCII on B cells had decreased Th2 cytokines IL-4 and IL-5 [152]. Also in another study it has been reported that B-cell-derived exosomes can present allergen peptides and activate allergen-specific T cells to proliferate and produce Th2 cytokines IL-5 and IL-13 [42]. 

Basophils Drive Th2-Cell Differentiation through Secretion ofTh2 Cytokines and Antigen Presentation... 

Interleukin-10 (IL-10) affects antigen presentation capacity but also interferes with many other functions of monocytes and macrophages (Table 2) (F8). In vitro, IL-10 is a potent inhibitor of cytokine production, including production of TNF, IL-1, IL-6, and IL-8 by LPS-activated monocytes/macrophages (F8). It also inhibits tissue factor-dependent procoagulant activity induced by LPS in human... 

It is clear that the type 2 cytokines IL-4, IL-9 and IL-13 play an obligatory role in host resistance to nematode infection whereas type 1 responses promote host susceptibility. Therefore, given that susceptibility to nematode infection is not due to a lack of responsiveness perse, but rather the development of an inappropriate response, it is important to understand the factors that influence the induction and expansion of Th subset responses and so control infection outcome. Studies in nematode models and other systems have addressed these questions and identified the importance of host genetic factors, the nature of the antigen and the antigen presenting cell, co-stimulatory molecules on these cells, and the cytokine and chemokine environment immediately following induction of the response. 

Cells of the T cell lineage appear to be more sensitive to the immunomodulatory effects of Pb compared to other lymphoid populations. In addition, there are considerable differences in sensitivity across various T cell subpopulations [38 41], This differential sensitivity has become another major hallmark of Pb-induced immunotoxicity, although most data implicate T cells as indirect targets of Pb immunotoxicity. Both in vivo and in vitro observations of T-dependent immune responses in the presence of Pb suggest that T helper function and Th-dependent cytokines are skewed preferentially toward Th2 reactivities. Smith and Lawrence [42] found that Pb inhibited antigen presentation and stimulated a T cell clone of the Thl phenotype. McCabe and Lawrence [38] were the first to show that Pb inhibited Thl stimulation while it promoted presentation to Th2 clones. Heo and colleagues [39 41] provided both in vitro and in vivo results supporting this immunomodulation by Pb. 

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