TCR cross-reactivity and allorecognition: new insights into the immunogenetics of allorecognition

Alloreactive T cells are core mediators of graft rejection and are a potent barrier to transplantation tolerance. It was previously unclear how T cells educated in the recipient thymus could recognize allogeneic HLA molecules. Recently it was shown that both naïve and memory CD4+ and CD8+ T cells are frequently cross-reactive against allogeneic HLA molecules and that this allorecognition exhibits exquisite peptide and HLA specificity and is dependent on both public and private specificities of the T cell receptor. In this review we highlight new insights gained into the immunogenetics of allorecognition, with particular emphasis on how viral infection and vaccination may specifically activate allo-HLA reactive T cells. We also briefly discuss the potential for virus-specific T cell infusions to produce GvHD. The progress made in understanding the molecular basis of allograft rejection will hopefully be translated into improved allograft function and/or survival, and eventually tolerance induction

Toughness of graphs and the existence of factors

AbstractThe toughness of a graph G, denoted by t(G), is defined as the largest real number t such that the deletion of any s vertices from G results in a graph which is either connected or else has at most s/t components.Chvátal who introduced the concept of toughness in [2] conjectured that if G is a graph and k a positive integer such that k |V(G)| is even and t(G)⩾k then G has a k-factor. In [3] it was proved that Chvátal's conjecture is true. The main purpose of this paper is to present two theorems which imply the truth of Chvátal's conjecture as a special case

SUT Journal of Mathematics Vol. 41, No. 1 (2005), 1–10 Edge-connectivity and the orientation of a graph

Abstract. Let G be a k-edge-connected graph and let L denote the subset of all vertices having odd degree in G. For every subset K = {u1, u2,..., uk} of L with |K | ≤ |L|, and for every function h defined on K having the property that j ‰ 2 ı — �ff dG(ui) dG(ui) h(ui) ∈ for all ui ∈ K, there exists an orientation