Characterization of the human cellular immune response to purified group A streptococcal blastogen A

The human mononuclear cell response to purified extracellular streptococcal protein, blastogen A, was compared to the response of these cells to PHA and tetanus antigen. Blastogen A induced peak uptake of thymidine during day 6 of tissue culture whereas PHA induced peak uptake during day 5 and tetanus during day 8. Like PHA, blastogen A transformed human umbilical cord lymphocytes and those of nonimmune animals. Also like PHA, blastogen A transformed primarily T lymphocytes. However, unlike PHA, the ability of T lymphocytes to respond to blastogen A was almost completely dependent on the presence of viable non-T lymphocytes. Monocytes were not as effective in facilitating the response to blastogen A as they were for PHA. Thus, blastogen A behaves most like a polyclonal T lymphocyte mitogen, although the degree of dependence of the transformation response on the presence of non-T lymphocytes is much greater than that of PHA.