The use of post-source decay in matrix-assisted laser desorption/ionisation mass spectrometry to delineate T cell determinants

The identification of naturally processed peptides presented by molecules o f the major histocompatibility complex (MHC) has progressed significantly o ver the past decade. The elution of peptides from immunoaffinity purified c omplexes of MHC class I or class II molecules has provided highly specific biochemical information regarding the nature of endogenous peptides capable of binding to and bring presented by particular MHC alleles. Whilst Edman chemistry is sufficient for the identification of abundant or homogeneous i mmunodominant peptides contained in samples of fractionated peptides, mass spectrometry has proved more powerful for sequencing less abundant species present in the typically heterogeneous fractions of eluted peptides. This r eview focuses on the characterisation of T cell determinants by matrix-assi sted laser desorption/ionisation (MALDI)-time-of-flight (TOF) mass spectrom etry (MS). We demonstrate, with specific examples, the utility of post-sour ce decay in MALDI-TOF MS for the characterisation of the amino acid sequenc es of both native and modified T cell determinants. The potential advantage s and pitfalls of this technique relative to the more commonly used forms o f tandem mass spectrometry in electrospray and ion spray modes of ionisatio n as well as hybrid quadrupole-quadrupole-TOF instruments are discussed. We highlight the complementarity between these techniques and discuss the adv antages in the combined use of both MALDI- and electrospray-based instrumen tation in epitope identification strategies. (C) 2001 Elsevier Science B.V. All rights reserved.