CD8 lymphocytosis in primary cytomegalovirus (CMV) infection of allograft recipients: expansion of an uncommon CD8+ CD57- subset and its progressive replacement by CD8+ CD57+ T cells.

Allograft recipients undergoing cytomegalovirus infection present increased proportions of circulating CD8+ lymphocytes. A longitudinal study of 11 kidney and five liver allograft recipients with primary CMV infection but no other etiological factor of graft dysfunction revealed selective imbalances of peripheral blood CD8+ T cell subsets. Initially, CMV viraemia is associated with elevated CD8+bright T cell numbers and T cell activation. Activation markers fall to normal when viral cultures become negative (before the end of the first month). During the second to sixth month, most (12/16) patients keep up high CD8+ T cell counts (1050-2900 CD8+ cells/mm3), comprising an uncommon CD8+ T cell subset, as 45-73% of CD8+bright lymphocytes were CD3+ and TCR alpha beta+, but were not stained by anti-CD28, CD11b, CD16, CD56, and CD57 antibody. Unexpectedly, CD8+CD57+ T cells, a hallmark of CMV infection, do not appear until the second to sixth month of primary CMV infection, and their numbers increase progressively thereafter. They become the predominant CD8+ T cell subset after 6 months of infection and their persistence for several (up to 4) years is strongly correlated (r = 0.87) with expansion of CD8+ cells. By analysis with MoAbs, there was no bias towards the use of particular TCR-V beta gene families at any time of primary CMV infection. Persistence of CD8 lymphocytosis is thus directly related to the rate of expansion of an uncommon CD8+CD57- subset and its progressive replacement by CD8+CD57+ T cells that are chronically elicited by CMV.