Additional evidence that the cell-associated immune system is the primary host defense against measles (rubeola)

Indirect evidence, such as the ability of agammaglobulinemic children to respond normally to measles and the inability of thymic-deficient children to survive measles led Burnet to postulate that the cell-associated immune system is the primary host defense against measles. Using a classical leukocyte culture system, which measures 3 H-thymidine incorporation as its endpoint, we have recently described an in vitro assay for lymphocyte responsiveness to measles complement fixation antigen (CFA) that has allowed us to study this question directly. Two pediatric residents who had negative HIA titers against measles and who had frequent exposure to measles were tested using this assay. Neither resident has had clinical measles or atypical measles syndrome. Both subjects displayed strong cellular responsiveness to measles in this system. We feel that the lymphocyte responsiveness to measles CFA seen in these residents is the in vitro correlate of their clinical protection against measles and offers additional evidence for the fundamental role of cell-associated immunity in the host's response to common viral infections.