%0 Journal Article
%T The Major Histocompatibility Complex in Transplantation
%A Marco Antonio Ayala Garc¨ªa
%A Beatriz Gonz¨¢lez Yebra
%A Andrea Liliana L¨®pez Flores
%A Eduardo Guan¨ª Guerra
%J Journal of Transplantation
%D 2012
%I Hindawi Publishing Corporation
%R 10.1155/2012/842141
%X The transplant of organs is one of the greatest therapeutic achievements of the twentieth century. In organ transplantation, the adaptive immunity is considered the main response exerted to the transplanted tissue, since the principal target of the immune response is the MHC (major histocompatibility complex) molecules expressed on the surface of donor cells. However, we should not forget that the innate and adaptive immunities are closely interrelated and should be viewed as complementary and cooperating. When a human transplant is performed, HLA (human leukocyte antigens) molecules from a donor are recognized by the recipient's immune system triggering an alloimmune response Matching of donor and recipient for MHC antigens has been shown to have a significant positive effect on graft acceptance. This paper will present MHC, the innate and adaptive immunities, and clinical HLA testing. 1. Introduction The primary function of the immune system is to protect the host from infectious microbes in its environment. This system has evolved over millions of years, in response of coexistence with microorganisms. Basically, the system can be divided in two components, the innate and adaptive immunities. 2. Innate and Adaptive Immunities The innate also called natural immunity refers to a nonspecific response that involves the recruitment of diverse components of the immune system such as macrophages, neutrophils, natural killer cells (NK cells), cytokines, several cellular receptors, complement components, cytokines, Toll-like receptors (TLRs), and antimicrobial peptides (AMPs). This response is phylogenetically older in comparison to the adaptive immunity, which involves recognition of specific antigen, conferring both specificity and a memory effect [1]. The main effectors of the adaptive immunity are the T and B cells. T cells recognize antigen in the form of peptide bound to major histocompatibility complex (MHC) molecules [2]. B cells have immunoglobulin receptors that recognize the antigenic portions of determined molecules [3]. In organ transplantation, the adaptive immunity is considered the main response exerted to the transplanted tissue, since the principal target of the immune response is the MHC molecules expressed on the surface of donor cells. However, we should not forget that the innate and adaptive immunities are divided only by educational purposes, since both are codependent. For example, T-cell activation leads to the production of cytokines and chemokines which in turn may recruit components of the innate immunity like NK cells or
%U http://www.hindawi.com/journals/jtrans/2012/842141/