Effects of heterologous anti-lymphocyte serum on the distribution of 51-Cr-labelled lymph node cells in mice.

The effects of heterologous anti-lymphocyte serum (ALS) were studied in a syngeneic cell transfer system, in which lymph node cells from donor CBA mice were labelled with Cr and transferred intravenously into syngeneic recipients. Labelled cells treated with ALS were unable to migrate to lymph nodes or spleens of recipients, as did normal cells, but instead distributed themselves very similarly to cells which had been killed by exposure to heat. It is thus likely that cells treated with ALS are killed after transfer by the cytotoxic action of ALS mediated by the complement of the recipient. ALS administered directly to the recipients of labelled lymphocytes could also reduce their uptake into lymphoid tissue; however, the magnitude of this effect appeared to be critically dependent upon the timing of the antiserum dose with respect to the labelled cell dose. ALS given immediately prior to labelled cells showed the greatest effect, while treatment given either 24 hours before or after the labelled cells was much less effective. While with prior treatment the reduced effect could be due to a fall off in antibody titre during the interval between the dose of antiserum and cells, in the latter situation no drop in titre would have occurred. It thus seems that lymphocytes that have already established themselves in lymphoid tissue may be less susceptible to the action of ALS. ALS given chronically to lymphoid cell donors resulted in a population of cells which upon transfer to normal recipients were distributed differently from either normal or NRS-treated donor cells. These data support the hypothesis that the effects of ALS may be exerted preferentially on circulating lymphocytes, and that ALS may act to selectively reduce the representation of this cell type in lymphoid tissue.