T-Cell Membrane CD45RA (2H4) and CD45RO (UCHL1) Determinants: I, Diverse Patterns of Expression in Mature (Post-Thymic) T-Cell Proliferations.

Abstract

By simultaneous two- and three-colour flow cytometry, this study analysed the expression of membrane CD45RA (2H4) and CD45RO (UCHL1) determinants by normal thymocytes (n = 5) and peripheral blood lymphocyte subpopulations (CD4(+), n = 21; CD8(+), n = 12; CD8(dim+), n = 12) and compared these patterns with those of T-cells from representative CD4(+)CD8(-) (n = 8), CD4(+)CD8(+) (n = 2), CD4(-)CD8(+) (n = 10) and CD4(-)CD8(-) (n = 1) proliferations. These comprised cases of prolymphocytic leukaemia (T-PLL, n = 5), adult T-cell leukaemia-lymphoma (ATLL, n = 2), Sezary Syndrome (SS, n = 4), chronic lymphocytic leukaemia (T-CLL, n = 4), and lymphoproliferative disease of granular lymphocytes (LDGL, n = 5). Normal thymocyte fractions, of which a mean of 85% cells co-expressed membrane CD4 and CD8, were predominantly (mean 89%) 2H4(-)UCHL1(+) with the remaining cells consisting of 2H4(int)UCHL1(+) and 2H4(+)UCHL1(-) components. Further analysis showed that virtually all CDla(+) thymocytes were UCHL1(+) whereas the CD1a(-) fraction comprised similar proportions of both UCHL1(-) and UCHL1(+) subpopulations. Similarly, normal blood CD4(+), CD8(+) and CD8(dim+) lymphocytes showed reciprocal CD45RA/CD45RO expression and could be phenotypically grouped into 2H4(+)UCHL1(-) 2H4(int)UCHL1(+) and 2H4(-)UCHL1(+) subpopulations. Mean proportions of 48% and 68%, for CD4(+) and CD8(+) lymphocytes respectively, showed a composite 2H4(+)UCHL1(-) phenotype, whereas the percentage of NK-associated CD8(dim+) cells with this phenotypic pattern was considerably higher (mean, 85%). Normal lymphocyte subpopulations lacking both determinants (2H4(-)UCHL1(-)) were only rarely noted. Comparing normal patterns of CD45RA/CD45RO expression with those of the T-cell proliferations revealed diverse and abnormal patterns of staining for 3/6 of the CD4(+)CD8(-) SS and ATLL, and for 5/5 of the T-PLL (CD4(+)CD8(-), n = 2; CD4(+)CD8(+), n = 2; and CD4(-)CD8(+), n = 1) cases studied. In contrast, the nine cases of CD4(-)CD8(+) T-CLL and LDGL all showed CD45RA/CD45RO staining patterns similar to that of normal CD8(+)/CD8(dim+) blood lymphocytes (i.e. a predominance of 2H4(+)UCHL1(-) cells). Although the variant CD45RA/CD45RO pattern types of the CD4(+) proliferations did not appear to be related to either the diagnostic category or other phenotypic characteristics, the high proportion of abnormal patterns within this case group suggests that recognition of these abnormalities may be potentially relevant to the differentiation of benign and malignant CD4(+) proliferations and, in addition, may be of aetiological importance with respect to the diverse acquired defects in immunity commonly seen in patients with such disorders.