"Self-reactive" T cells. III. In vitro restimulation of T cells, "responding" in vivo or in vitro to syngeneic lymphoid cells

Polyclonally activated lymphoblasts, transferred to syngeneic recipient mice, elicited a host T-cell-mediated "response" in vivo. These T cells, which "responded" in vivo to syngeneic lymphoblasts (i.e. in vivo primed "responder" T-cell population), acquired the capacity to "stimulate" a "response" of syngeneic T cells in vitro in a syngeneic one-way mixed lymphocyte culture, S-MLC (i.e. in vitro primed "'responder" T-cell population). We now describe the presence of memory and specificity in these two types of "self-reactive""responder" T-cell populations. This is investigated in in vitro "restimulation" experiments with mitomycin-blocked syngeneic and allogeneic lymphoid cells of various origin. "Self-reactive" T cells could be restimulated repeatedly (over many weeks) with mitomycin-blocked syngeneic lymphoid-cell populations, but not with mitomycin-blocked allogeneic normal spleen cells. "Self-reactive" T cells "responded" to syngeneic large activated lymphoblasts, as well as to syngeneic small resting lymphocytes. We found no "responder" T-cell reactivity specific for the mitogen that induced syngeneic "stimulator" cell populations. Both populations of "self-reactive" T cells displayed reactivity to mitogen-induced allogeneic lymphoblasts.

"Self-reactive" T cells. II. Transferred syngeneic lymphoblasts induce T "stimulator" cells in vivo, to which syngeneic T cells "respond" in a syngeneic MLC in vitro

Splenic T cells, engaged in an in-vivo "response" to transferred syngeneic lymphoblasts, displayed an extensive proliferative activity if cultured in vitro. These cells (blocked by mitomycin C) were "stimulator" cells in a one-way syngeneic mixed lymphocyte culture (S-MLC). "Responder" cells were derived form spleens of syngeneic (sex and age matched) mice. Fractionation studies showed that "stimulator" and "responder" cells in the investigated S-MLC were nylon-wool non-adherent and sensitive to treatment with anti-Thy-1 antiserum and complement, i.e. were cells of the T lineage. Coculture experiments demonstrated that direct cell contact is required to trigger a proliferative "response" in the S-MLC. Fetal calf serum-supplemented tissue-culture medium supported "responder" cell proliferation, normal mouse serum-supplemented medium did not. The in-vivo generation of a T-cell population, which could "stimulate" a syngeneic T-cell "response" in the S-MLC in vitro, was investigated.

"Self-reactive" T cells. I. In vivo reaction of T cells to transferred polyclonally activated syngeneic and autologous lymphoblasts

Polyclonally activated splenic lymphocytes (generated in mitogen-stimulated cultures) were transferred to syngeneic or autologous recipient mice. Injection of cells into the footpad of syngeneic recipients induced a regional response in the ipsilateral popliteal lymph node; intravenous cell transfer elicited a systemic splenomegaly reaction. These reactions displayed a linear log number of transferred cells/response relationship in syngeneic and autologous systems. The kinetic and magnitude of the regional response to syngeneic lymphoblasts ands to allogeneic spleen cells were comparable. No difference was apparent in the phenomenology of the in-vivo responses to syngeneic lymphoblasts induced by various T- or B-cell mitogens. The in-vivo response was: 1. stimulated by large-size lymphoblasts; and 2. mediated by host T cells. Data excluded a direct involvement of mitogen or heterologous serum constituents in tissue culture medium in the described reaction. Experimental evidence argues against the involvement of virus components in the observed phenomenon.

In vitro proliferation of haemopoietic cells in the presence of adherent cell layers. II. Differential effect of adherent cell layers derived from various organs

Mouse bone marrow-derived adherent cell populations promoted proliferation of haemopoietic cells in vitro in a liquid culture system for at least 4 weeks. Adherent cell layers derived from other haemopoietic organs (foetal liver, adult spleen) and fibroblasts from embryonic tissues did not maintain haemopoietic cells in this system. Medium, conditioned by adherent cells derived from foetal liver, spleen and embryonic tissues displayed a considerable colony stimulating activity (CSA). Marrow-derived adherent cells produced no detectable CSA. A possible relationship between the in vitro expression of a growth-promoting activity of an adherent cell population on haemopoietic cells, and its endogenous CSA production, is discussed.

In vitro proliferation of haemopoietic cells in the presence of adherent cell layers. I. Culture conditions and strain dependence

The culture system, in which a marrow-derived adherent cell population, established in vitro, exerts a long-term promoting influence on proliferation of haemopoietic cells, is reproduced. Essential parameters of the system are investigated; it is confirmed that the system is critically dependent on horse serum, and on the in vitro age of the adherent cell layer. The growth-promoting effect on haemopoietic cells seems to be independent of the number of marrow cells per culture flask initially inoculated into the cultures to establish the adherent cell layer. In vitro established marrow-derived adherent cell layers from RFM (H-2f) and BALB/c (H-2d) mice can promote the long-term proliferation of syngeneic and allogenic haemopoietic cells; haemopoietic marrow cells from C3H (H-2k) cannot be maintained on syngeneic or allogeneic (BALB/c, H-2d) adherent cell layers; adherent cell layers of C3H (H-2k) can maintain haemopoietic cells of the H-2d (BALB/c) genotype. This culture system does not reproduce the in vivo phenomenon of allogeneic resistance. The relevance of these findings to the suggestion that the growth-promoting activity of adherent marrow cells on haemopoietic stem cells in vitro duplicates aspects of the in vivo haemopoietic microenvironment is discussed.