"Warm" E rosettes as an index of activation of T lymphocytes

Rosetting at 37 degrees ("warm" rosettes) was assayed as a technique to determine the degree of activation of T lymphocytes. Standard "cold" rosettes and an index of "warm" to "cold" rosettes were used to correct possible changes in the total percentage of T cells. Statistically higher numbers of "warm" rosettes were obtained in Pokeweed mitogen stimulated cultures when compared with unstimulated control; but not in old tuberculin stimulated cultures of lymphocytes from PPD positive individuals when compared with those of PPD negative. Also a significant rise was found in control cultures of 3 and 5 days when compared with those of day 1. We think that "warm" rosetting may be a useful technique for determining the degree of immunological activation of a lymphocyte population.