Reduction of CD45RA Isoform Expression and Decrease in CD4 and CD8 Receptor Density in Lymphocytes of Patients with Primary Biliary Cirrhosis

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Abstract
Background: The immunological background of primary biliary cirrhosis (PBC) remains largely obscure. Methods: Using double colour flow cytometry, we estimated the distribution of functionally different lymphocyte subpopulations in the peripheral blood of 25 PBC patients and 18 controls. We examined: 1) the expression of CD3, CD4, CD8, CD 19 and CD56 surface receptors, 2) the distribution of lymphocyte subsets bearing ‘naive’ (CD45RA+) and ‘memory’ (CD45RO+) phenotypes in both CD4+ and CD8+ cell populations, 3) the expression of an early activation marker (CD69), 4) the distribution of C1.7 mAb binding cytotoxic effectors in CD3+, CD8+ and CD56+ cells. The surface marker expression was evaluated in terms of percentage of positive cells and receptor density. Results: We found: 1) a decrease in the percentage of total CD3+ and CD4+ cells, an unchanged proportion of CD8+ cells but elevated proportion of CD 19+ cells and NK lymphocytes; 2) a reduction in the percentage of ‘naive’ CD4+ but normal proportion of ‘naive’ CD8+ as well as CD4+ and CD8+ ‘memory’ cell subsets; 3) a decrease in the density of CD4 and CD8 receptors in the subsets of ‘naive’ and ‘memory’ T cells, 4) an increase in the percentage of CD69 receptor bearing T cells but unchanged proportion of C1.7 mAb. Conclusions: It is concluded that the reduction in number of 'suppressor-inducer-like ‘naive’ CD4+ T-cell subsets in association with the decrease in fluorescence intensity for CD4 and CD8 may significantly contribute to the mechanisms that could account for a development of PBC.