Regulatory effects of thymus humoral factor on T cell growth factor in aging mice

The effect of thymus humoral factor (THF) on T cell growth factor (TCGF) production by T cells and the association between splenic macrophages and T cells from young (2-3 months) and old (20-24 months) mice in this respect were studied. Splenocytes were divided into three groups: stimulated with concanavalin A (Con A); preincubated with THF and then stimulated with Con A; or stimulated with Con A and thereafter incubated with THF. These cells were then examined for production of TCGF. Cells treated with Con A and THF as described above were passed on nylon wool to enrich T cell populations and added to mitogen-sensitized (Con A or lipopolysaccharide) adherent splenocytes of old and young mice in the following combinations: young adherent and young T cells; young adherent and old T cells; old adherent and young T cells; and old adherent and old T cells. The results demonstrated that: (A) cells of old mice produced less TCGF than the young; (B) preincubation of splenocytes or nylon-wool enriched T cells with THF increased the production of TCGF consistently in young mice, whereas in the old a significant increase was observed only in some cases; (C) depressed TCGF activity was observed when treatment with THF to splenocytes or nylon-wool enriched T cells from young and old mice was performed after Con A stimulation, and this was also more pronounced in the young; (D) the reduced level of TCGF in the old seemed to be related to a lesion in the T cell compartment, since adherent cells from old and young mouse spleens could support TCGF production by T cells from young mice and not from old.