QUANTITATIVE AND QUALITATIVE CHANGES IN CD44 AND MEL-14 EXPRESSION BYT-CELLS IN C57BL 6 MICE DURING AGING/

Aging is associated with a decrease in the functional activity of T ce lls. We have explored age-related alterations in CD44 and MEL-14 expre ssion by spleen cells bearing the Thy1.2, CD4 or CD8 antigens in C57BL /6 mice at 2, 8, 15 and 23 months of age. The membrane expression of C D44 and MEL-14 molecules can be used to distinguish naive (CD44(low), MEL-14(high)) from preactivated/memory (CD44(high), MEL-14(low))T cell s. Our results show that the proportion of CD4(+) splenic cells begins to decrease at an intermediate age (8-month-old mice), whereas the pr oportion of CD8(+) cells remains unaltered. The proportion of CD4(+) a nd CD8(+) splenic cells with the CD44(high) memory phenotype was incre ased at an early stage of aging (in 8-month-old mice) without a concom itant change in MEL-14 expression. In older mice, MEL-14 expression de creased on CD4(+) but not on CD8(+) subsets. Recent studies have repor ted that following activation, the expression of CD44 molecules contai ning additional, so-called variable exons can be detected. By PCR, we observed an increase in CD44 transcripts containing the v6 or v7 varia ble exons in murine lymph nodes at the age of 15 months. Our results s uggest that v6- or v7-containing variants of CD44 may be involved in t he development of memory cells. Taken together, these results suggest that the trafficking of memory T cells in aging may be altered by quan titative and/or qualitative differences in the expression of molecules involved in lymphocyte recirculation.