Clinical significance of CD45RO expression on peripheral blood mononuclear cells in HTLV-I-infected individuals

The phenotype of peripheral blood mononuclear cells (PBMC) was examined in 13 healthy volunteers, 26 HTLV-I carriers, and 58 ATL patients (22 smouldering, five chronic, 24 acute, and seven lymphoma type). The percentage of CD4⁺, CD25⁺, CD28⁺ and CD45RO⁺ cells in the PBMC of the chronic and acute type patients was significantly higher than that of the volunteers, whereas the percentage of CD8⁺ and CD45RA⁺ cells in these patients was significantly low. The histogram for CD45RO fluorescence intensity (FI) revealed two patterns: pattern A consisted of CD45RO⁺ cells with high FI (CD45RO^high) and intermediate FI (CD45RO^int). Pattern B consisted exclusively of CD45RO^high. Pattern A was evident in all volunteers. The percentage of subjects showing pattern B was increased in an order that reflected disease progression. In the patients with pattern A, the CD45RO^int cells were CD4⁺ and CD8⁻, and the FI of CD2, CD3, and Fas within the CD45RO^int cells appeared to be lower than that within the CD45RO^high cells. The acute type patients with pattern A had a significantly longer survival curve than that of these patients with pattern B. These results suggest that the presence of CD45RO^int cells may be related to protection against disease progression in HTLV-I-infected individuals.