China
Africa
Explore chapters and articles related to this topic
Clinical Effects of Pollution
Published in William J. Rea, Kalpana D. Patel, Reversibility of Chronic Disease and Hypersensitivity, Volume 5, 2017
William J. Rea, Kalpana D. Patel
Depending on genetic susceptibility and the nature of the exposure, CBD occurs in up to 20% of exposed workers. Genetic susceptibility has been associated with particular HLA-DP alleles, especially those possessing a negatively charged glutamic acid residue at the 69th position of the beta-chain.
Head Transplantation: The Immune System, Phantom Sensations, and the Integrated Mind
Published in The New Bioethics, 2018
In the vocabulary of immunology, the expressions ‘self’ and ‘non-self’ may be thrown about with such abandon that these expressions are easily used to conflate issues in the broader language of personhood. It is important, therefore, to remember that when these expressions are used in immunology they are concerned with molecular recognition. The immune system consists of a network of molecular and cellular systems that undertake the critical function of differentiating that which is described in immunological terms as ‘self’ from that which is ‘non-self’ and imposes a level of identity on cells and tissues that must be considered in any transplant operation. These systems are typically grouped under the general headings ‘innate immunity’ and ‘adaptive immunity’ and involve more than 1600 genes (Abbas et al. 2005). Underpinning the adaptive responses are protein complexes brought together under the general heading the ‘major histocompatibility complex’ (MHC), also referred to as ‘human leukocyte antigens’ (HLA) when specific human MHC proteins are being referenced. MHC antigens are grouped into a number of classes, which, in broad terms, might be said to share function, insofar as they may, for example, process proteins into small chunks that are then presented to the T-cell receptor (TcR) on T-cells (La Gruta et al. 2018). They do, however, differ structurally from each other and serve different specific tasks. One of these, MHC class I (MHC-I, of which HLA-A, HLA-B, and HLA-C are members), is normally present on all nucleated cells, and subclasses of this are expressed within the first three days of the life of a human embryo (Wang et al. 2009). The absence MHC-I expression on cells leaves them vulnerable to destruction through the action of the MHC-I-sensing ‘killer cell immunoglobulin-like receptor’ (KIR), present on subpopulations of immune cells known as Natural Killer (NK) cells and subsets of T-cells. An important exception to this is the red blood cell population. Red cells do not express MHC-I, instead escaping destruction by NK cells through the expression of another protein, CD47 (Wang et al. 2010). Alongside the MHC-I, the expression of MHC class II (MHC-II, comprising HLA-DP HLA-DQ and HLA-DR in humans) and minor histocompatibility antigens (MiHA) like the male-specific H-Y antigen. The result of this is that, by the 8-cell stage of the embryo, the embryo is immunologically reactive with respect to the mother and its continued development requires the induction of immunological tolerance within the womb to prevent fetal rejection and miscarriage (Fernandez et al. 1999; Larsen et al. 2013; Colucci 2017).