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Cellular Biology in Tissue Engineering
Published in Joseph W. Freeman, Debabrata Banerjee, Building Tissues, 2018
Joseph W. Freeman, Debabrata Banerjee
Rejection cannot be completely prevented; however, a degree of immune tolerance to the transplant does develop. Tissue typing or cross-matching is performed prior to transplantation to assess donor-recipient compatibility for human leukocyte antigen (HLA) and ABO blood group and to ensure the safety of the procedure. There are several tests that can be executed. In one of the first tests, the ABO blood group compatibility is tested because incompatibility between the blood groups leads to rapid rejection. As always, it is important to monitor the patients with proper immunosuppressive treatment. Lastly, mixed lymphocyte reaction (MLR) can be used to assess the degree of MHC class I and class II compatibility. However, it is not a rapid test and can be used only in cases involving living related donors. It is rarely used at present.
Immune Responses
Published in Ronald Fayer, Lihua Xiao, Cryptosporidium and Cryptosporidiosis, 2007
Depending on the nature of the antigens that the immune system encounters, CD4+ T helper (Th) cells may induce a cell-mediated immune response (Th1) or antibody-mediated response (Th2). These diverse Th responses are determined by the spectrum of cytokines produced by the T-cells themselves and by the antigen-presenting cells. In a Th1 response, IL-12 produced by dendritic cells and macrophages drives the T-cells to produce IFN-?. This type of response is usually required to control and eliminate intracellular infections. In a Th1 response, CD8+ cytotoxic T-cells may also be induced with or without help from CD4+ T cells. These cells kill infected cells in an MHC class I-restricted fashion. A Th2 response is associated with production of IL-4, IL-5, IL-9, and IL-13, and polarized Th2 responses are observed in allergies and asthma; they may also be required to eliminate helminth infections (Wynn, 2003). The Th1 and Th2 pathways can oppose each other as Th1 responses are inhibited by Th2 cytokines such as IL-4 and IL-13 and, similarly, Th2 development is inhibited by Th1cytokines. Recently, another Th response associated with inflammation has been characterized. Th17 cells are induced by the IL-12-related cytokine IL-23, and they produce IL-17, IL-6, and TNF-a (Weaver et al., 2006). This response occurs in autoimmune diseases, but its involvement in immunity to infection is less clear.
A mathematical model of cytotoxic and helper T cell interactions in a tumour microenvironment
Published in Letters in Biomathematics, 2018
Heidi Dritschel, Sarah L. Waters, Andreas Roller, Helen M. Byrne
There are two populations of T cells, helper and cytotoxic, which are distinguished by their expression of CD4 and CD8 proteins, respectively. Naive helper T cells are activated by antigen presented with a major histocompatibility complex (MHC) class II molecule. (A glossary of the terminology used in this article is provided in Appendix 1.) Naive cytotoxic T cells are activated by antigen presented with an MHC class I molecule. Once activated the helper and cytotoxic T cells perform complementary functions to eliminate the tumour. Helper T cells further differentiate into subpopulations classified by the specific cytokines that they produce. In this way, they regulate multiple aspects of an immune response. For example, they promote the proliferation of cytotoxic T cells, they recruit and promote cells of the innate immune response, and they control levels of inflammation at the tumour site (Hung et al., 1998; Magombedze et al., 2013). (In this work, we do not distinguish these subpopulations.) Cytotoxic T cells scan the body for transformed cells (cancer cells) to which they bind before inducing cell killing.