Lymphocyte cultures with small numbers of cells: antigenic stimulation by histoplasmin

Previous experiments from this laboratory have shown that small numbers of lymphocytes could be stimulated by phytohemagglutinin to transform. Experiments in 15 subjects sensitized to histoplasmin demonstrated that antigenic stimulation with histoplasmin could be achieved with as few as 12.5 X 10(3) lymphocytes per 0.1 ml culture, (2,521 +/- 1.260) compared to unstimulated cultures (250 +/- 41), p less than 0.01, although false negative values (less than three fold increase in radionucleotide incorporation over unstimulated cultures) were obtained in 6 of 15 cases. Fourteen of 15 positive responders were correctly identified by culturing 25 X 10 (3) cells with histoplasmin for six days. The cell numbers required to give a blastogenic response with histoplasmin can be reduced to 25 X 10(3) cells in situations where cell availability is limited.