Heterogeneity of the cytotoxic response of thymus-derived lymphocytes after immunization with influenza viruses.

Immunization of mice with serologically distinct type A influenza viruses results in development of highly crossreactive populations of cytotoxic thymus-derived lymphocytes (T cells). This can be shown both at the level of effector function and of priming for an enhanced response after challenge with another type A virus. Cytotoxic activity is demonstrable, in both the primary and secondary situations, only for H-2 compatible interactions. Further analysis by competitive inhibition experiments indicates that some of the T cell clones generated are specific for the virus used to immunize, while others are much less restricted. Secondary stimulation may result in preferential stimulation of the crossreactive T cells if the type A viruses used are very different serologically. When more closely related viruses are used, however, some degree of specificity is seen for the challenge virus. Even so, the patterns of crossreactivity observed are complex, and cannot be readily predicted on the basis of known serological relationships between surface hemagglutinin and neuraminidase antigens of type A influenza viruses.