A cell-saving non-radioactive limiting dilution analysis-assay for the combined determination of helper and cytotoxic T lymphocyte precursor frequencies.

We have developed a limiting dilution analysis-assay which makes the determination of both helper and cytotoxic T lymphocyte precursor frequencies possible. The way in which T helper precursor frequencies are determined in this combined assay is essentially the same as the method published previously. Experimental conditions for the combined assay have been optimized to obtain cytotoxic T lymphocyte precursor frequencies that are comparable to those determined in the assay routinely used in our laboratory. For all situations where the amount of available cell material is a limiting factor, it will be an advantage that with the same number of cells needed for a standard cytotoxic T lymphocyte precursor frequency determination, in the combined assay both helper and cytotoxic T lymphocyte precursor frequencies can be determined. This is especially convenient in the case of bone marrow transplantation, where evidence is accumulating that low or negative cytotoxic T lymphocyte and/or T helper precursor frequencies may be a prerequisite for a successful transplantation with a minimal risk of graft-versus-host disease.