Cell components in the immune response: IV. Relationships and possible interactions

Abstract

In the previous papers in this series it was shown that mouse spleen cell populations could be separated into various subpopulations that were less responsive to sheep erythrocytes in an in vitro culture system. Attached and nonattached cells were separated by differential attachment to glass and plastic surfaces and A- and D-band populations were obtained as light and dense cell populations on an albumin density gradient. In this paper it is shown that attached and A-band cells are equally effective in their ability to restore the response of precursor cells present in either the nonattached or D-band populations. This restorative activity is not abolished by X-irradiation. Cell-free culture supernatant fractions of the attached cells also gave significant restoration of the response in many but not all of a series of experiments. These observations are discussed and are compared with the recent findings of other workers. It is suggested that the findings are compatible with a three-cell model of cellular interaction in the initiation of the immune response but do not of themselves establish such a theory. It is pointed out that the factors which were demonstrated might equally well affect the proliferative phase of the response and produce their effects by variation in the number of antibody-forming progeny which could be obtained from a single stimulated precursor.