Primitive Vertebrate Immunity: What is the Evolutionary Derivation of Molecules that Define the Adaptive Immune System?
- Joan Marsh Organizer and
- Jamie A. Goode
Published Online: 28 SEP 2007
Copyright © Ciba Foundation 1994
Ciba Foundation Symposium 186 - Antimicrobial Peptides
How to Cite
Flajnik, M. F. (2007) Primitive Vertebrate Immunity: What is the Evolutionary Derivation of Molecules that Define the Adaptive Immune System?, in Ciba Foundation Symposium 186 - Antimicrobial Peptides (eds J. Marsh and J. A. Goode), John Wiley & Sons, Ltd., Chichester, UK. doi: 10.1002/9780470514658.ch13
- Published Online: 28 SEP 2007
Print ISBN: 9780471950257
Online ISBN: 9780470514658
- primitive vertebrate immunity;
- evolutionary derivation;
- adaptive immune system;
- major histocompatibility complex
The adaptive immune system is capable of responding to an infinite number of antigens with the antigen-specific receptors immunoglobulin (Ig) and the T cell receptor (TCR). lg binds soluble antigens while TCR recognizes antigen bound in clefts of polymorphic self-encoded major histocompatibility complex (MHC) class I and class II molecules. All of these molecules are wholly or partially composed of lg superfamily domains. TCR and lg use V-set lg superfamily domains, always in heterodimeric forms, in antigen recognition. Although the ways in which TCR and Ig bind antigen are fundamentally different, the structure of the heterodimeric V domains is probably identical. The antigen-binding cleft of MHC proteins has a structure unlike lg superfamily domains, although several investigators have proposed that this cleft is evolutionarily derived from lg domains. We believe the MHC cleft is a primitive structure, perhaps related to the peptide-binding domains of intracellular chaperone proteins. A model is proposed whereby chaperone proteins were the primordial MHC molecules, presenting peptides derived from invariant proteins residing inside cells for recognition by lymphocytes with minimally diverse receptors. Such a system may be reflected today by the epithelial immune system, apparently governed by monomorphic MHC molecules and lymphocytes with unconventional antigen-specific receptors.