Immunology: Comparative Immunology of Mammals

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Abstract

The mammalian immune system comprises a complex, coordinated and finely controlled series of interactions involving cells and molecules which has evolved to protect the host against disease. Mammals consist of a highly diverse group of animals in which the immune system has been subjected to a variety of selective pressures. This is reflected in differences in the organisation and function of their immune systems, and is seen especially in those gene families characterised by complexity and polymorphism, such as those encoding immunoglobulins (Ig), T-cell receptors (TCR), major histocompatibility complex (MHC) molecules and natural killer (NK) cell receptors. The evolution of these components in a range of mammalian groups and species will be the main focus of this article. Key Concepts: The mammalian immune system has evolved to protect the host against disease. The system is complex, involving specialised tissues, cells, soluble mediators and membrane-bound molecules. The mammalian adaptive immune response is characterised by extreme specificity in terms of antigen recognition. This specificity is largely determined by genes encoding the major histocompatibility complex (MHC) molecules, immunoglobulins (Igs) and T-cell receptors (TCRs). Selection pressure by pathogens is believed to drive the generation of polymorphism in functional MHC genes. MHC molecules present antigen to TCR and some additionally interact with NK cell receptors. NK cells act as both effector and regulatory cells of the immune response. Different mammalian groups and species have evolved a wide range of strategies to cope with rapidly changing pathogens, all aimed at protecting the host from disease. Keywords: immunity; mammals; immunoglobulin; lymphocytes; evolution; NK cell receptors; MHC; TCR