Analysis of the Functional Potential of Mouse CD4+ T Cells Using a High-Efficiency Cloning System

In order to examine the functional potential of individual mouse CD4+ T cells selected, as far as possible, in a random manner, a high-efficiency cloning system driven by Con A was utilized. Under optimal conditions, cloning efficiencies of CD4+ cells of about 50% were regularly attained. Although the relative proportion of different TH subsets varied depending on the cloning conditions, the high cloning efficiency, coupled with the analysis of over 100 clones, allowed important conclusions to be drawn regarding the general construction of the mouse CD4+ T cell repertoire. (1) At least 50% of all mouse splenic CD4+ T cells have the potential to produce IL4, supporting the view that TH subsets arise by an instructional or regulatory mechanism, rather than by selection. (2) TH0 clones produce amounts of IL2 and IL4 similar to those produced by TH1 and TH2 clones, respectively, but secrete much lower quantities of IFN than TH1 clones. (3) A large proportion of TH2 clones secrete measurable amounts of IFN. (4) Lymphokine secretion patterns among CD4+ T cells are clearly not determined at random, since IL2 production is always accompanied by IFN production. (5) At least 50% of all mouse splenic CD4+ T cells have cytolytic capacity as shown by killing in a 20-hr assay, but only a proportion can also kill in 4-hr assays. Killing in 4-hr assays was strongly correlated with the ability to secrete IL2, regardless of whether IL4 was also secreted.