Flow cytometric and morphologic studies of HNK1+ (Leu 7+) lymphocytes in relation to cytomegalovirus carrier status.

CMV carrier status of healthy individuals causes a persistent increase in the numbers of lymphocytes expressing the HNK1 (Leu 7) antigen. We investigated this phenomenon by correlating HNK1 fluorescence intensity of the CD3+, CD4+, CD8+ and CD16+ lymphocytes with their morphology. The study was performed on 112 healthy individuals as a function of their CMV carrier status. To this end, the CD3+, CD4+, CD8+ and CD16+ lymphocytes were stratified into subsets with undetectable (-), weak (+) and strong (++) levels of HNK1 fluorescence intensity, as well as into subsets with low, intermediate or high perpendicular light scatter (PLS) signals. Among the CD3+, CD4+ and CD8+ lymphocytes. CMV carrier status was associated with significantly increased numbers of HNK1(+) and particularly HNK1(++) cells. Among the CD16+ lymphocytes, CMV carrier status increased only the HNK1(++) ones significantly. There were clear positive correlations between the PLS characteristics of the CD3+, CD4+, CD8+ and CD16+ lymphocytes and their HNK1 fluorescence intensity. Microscopic analysis of CD3+ lymphocytes sorted into HNK1(-), HNK1(+) and HNK1(++) fractions revealed that the percentage of those cells containing azurophilic granules and the numbers of such granules per cell increased in proportion to their HNK1 fluorescence intensity. Thus, CMV also interacts with the HNK1+ lymphocytes of its healthy carriers by increasing the level of expression of that antigen which is accompanied by increased granularity. Those granular lymphocytes may include cytotoxic cells which are involved in the control of viral replication.