Variability of sequential studies of lymphocyte blastogenesis in normal adults.

Sixteen healthy adults had serial studies of delayed-type skin test reactivity and in vitro lymphocyte blastogenesis to several antigens over a period of 7 months. In many subjects blastogenesis varied broadly from month to month without apparent cause. Responses to all antigens usually increased or decreased together on sequential testing. Blastogenesis to coccidioidin appeared to result largely from cross-reaction with histoplasmin. Humoral factors were not demonstrably responsible for these changes. Blastogenesis rose consistently and non-specifically in subjects following revaccination to vaccinia virus. These studies reflect the lymphocyte blastogenesis reaction as a dynamic equilibrium, subject to spontaneous variation, and responding non-specifically to stimuli such as vaccination. Whatever the causes for these changes, it is clear that serial determinations of blastogenesis response to various antigens do not carry the apparent consistency of the skin test response to that antigen, and single tests must be cautiously interpreted.