Histocompatibility antigen-activated cytotoxic T lymphocytes. II. Estimates of the frequency and specificity of precursors.

TLDR

The study used limiting dilution of mouse mixed leukocyte cultures to directly estimate the minimum frequency of CTL precursors for various antigens and showed that a single precursor undergoes 3–4 divisions to produce 8–16 CTLs upon activation. The frequency of alloreactive CTL precursors was high, with 4–15 cells per 10⁴ lymph node cells reactive to DBA/2 and at least 1–2 % of all CTL precursors responding to any H‑2 haplotype difference; frequencies for xenoantigens or TNP‑modified self were less than half, and only a minority of precursors were cross‑reactive to a third H‑2 haplotype.

Abstract

Using limiting dilutions of responding cells in mouse mixed leukocyte cultures, we obtained direct estimates of the minimum frequency of precursors of cytotoxic T lymphocytes (CTL.P) for a variety of antigens. Depending on the strain combination, there were as many as 4-15 CTL.P reactive to DBA/2 among 10(4) lymph node cells. Taking into account that only 5-10% of peripheral T lymphocytes have the potential to develop into cytotoxic T lymphocytes (CTLs) (6), this implies that at least 1-2% of all CTL.P are responsive to any given H-2 haplotype difference. Precursors of cytotoxic cells thus have the same high frequency of cells reactive to alloantigens of the major histocompatibility complex as found among proliferating cells in graft-vs.-host reactions and mixed lymphocyte interactions. The frequencies of CTL.P reactive to xenoantigens (rat) or trinitrophenyl-modified self were less than half the frequency of alloreactive CTL.P. A minority of the CTL.P specific for one H-2 haplotype were also reactive to a third party H-2 haplotype, presumably on the basis of recognition of shared determinants. By dilution of sensitized cells from single microcultures, it was shown that a single CTL.P undergoes a minimum of three to four cell divisions and generates at least 8-16 CTLs after antigenic activation.