FACTORS INFLUENCING GROWTH OF PARENTAL MARROW GRAFTS IN IRRADIATED F1 HYBRID MICE

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Abstract
Transplantation of mor -phological intact spleen slice grafts from parental to F1 hybrid mice prior to lethal irradiation markedly improved the growth of subsequent parental marrow grafts. Stromal elements are not responsible for the improved marrow growth since similar results were obtained when the F1 hybrid was pretreated with parental spleen cell suspensions or spleen slice grafts which were removed before irradiation. Pre-treatment of hybrids must be done with immunologically competent cells; these cells must be viable; time is required for full development of the pretreatment effect, 2-3 wks. being optimal for 3 x 107 spleen cells; the effect is long lasting (at least 3 mo.); pretreatment with as few as 106 parental spleen cells can significantly modify the poor growth phenomenon. Augmentation of marrow growth was observed in every experimental setting where a graft-versus-host reaction due to cells from the marrow donor strain had occurred prior to irradiation. Relatively good growth of parental marrow grafts was observed in reirradiated old chimeras when either chimeric donor or host was of the parental type.