Immunological unresponsiveness and apoptotic cell death of T cells in measles virus infection

The phenotypic alterations associated with T cells during measles virus infection have been demonstrated and an attempt has been made to show programmed cell death (PCD) of T cells activated in vivo. During the acute phase of illness, activated T cells increased rapidly. Memory T cells (CD45RO⁺), especially CD8⁺ memory T cells also tend to increase. During the recovery phase, CD8⁺ T cells declined rapidly, and naive (CD45RA⁺) T cells increased in numbers. The anti-CD3 monoclonal antibody-induced expression of interleukin-2 receptor (CD25) was suppressed. However, the addition of phorbol 12-myristate 13-acetate (PMA) caused the significant recovery of CD25 expression. In addition, PCD of activated T cells from measles patients was induced in culture. After triggering of the T cell receptor-CD3 complex, cells became more susceptible to PCD. Interestingly, the addition of PMA could inhibit PCD of activated T cells. Taken together, these data suggest unresponsiveness and activation-induced cell death of T cells during the primary response to measles virus antigens, depending on the activation status of protein kinase C.