Allograft Response in Vitro

114

The effects of soluble concanavalin A (Con A) or Con A-activated spleen cells on the generation of cytotoxic lymphocytes (CL) in mixed leukocyte cultures (MLC) were examined. Mitogenic concentrations of soluble Con A or small numbers of Con A-activated spleen cells substantially inhibited CL responses. The suppression was partial rather than absolute and was critically dependent upon the concentration and time of addition of soluble Con A or Con A-activated spleen cells to the MLC. Suppressive effects of Con-A activated spleen cells were mediated by T cells since suppressor cell activity was abrogated by treatment of spleen cells with anti-θ serum and complement before or after Con A activation. X irradiation of spleen cells before Con A treatment also abrogated generation of suppressor cell activity. After activation by Con A, however, the function of suppressor cells was radioresistant. Although the precise mechanism(s) of suppression is, as yet, unknown, the precursors of CL must be exposed to Con A-activated cells during the early phases of the immune response for suppression to occur. Kinetic studies revealed that suppression of CL responses was not due to a failure to initiate an immune response, but represented a response which developed initially, but subsequently aborted. The relevance of these observations to the concepts of T-cell-T-cell interaction and regulatory control of immune responses by T cells is discussed.

mentioning

confidence: 72%

Cell-Mediated Immune Responses in Vitro

Peavy

Pierce

1974

114

“…Their data demonstrated that although suppressor T cells inhibited PFC responses only if present during the inductive phase of the response, suppression was not expressed until the later phase of exponential PFC proliferation. The development of primary cytotoxic lymphocyte responses in vitro is thought to require initial proliferation during the sensitizing MLR (35,36), although it is probable that the T-cell population responding in MLR is different from that which expresses cytotoxicity (37,38). Therefore, activated suppressor cell effects documented in studies of killer cell generation (8) may reflect suppression either of requisite proliferation in the sensitizing phase or of postproliferative differentiation of cytotoxic lymphocytes.…”

Section: Discussionmentioning

confidence: 99%

Regulatory Mechanisms in Cell-Mediated Immune Responses

Rich

1974

125

Regulatory effects of alloantigen-activated thymus-derived lymphocytes in mixed lymphocyte reactions have been demonstrated. Mice were injected into foot pads with allogeneic spleen cells; 4 days following sensitization spleen or regional lymph node cells from these animals were treated with mitomycin C and incorporated into MLR as regulator populations syngeneic to the responder cell type. Activated spleen cells suppressed MLR responses 60–90% whereas activated lymph node cells from the same animals enhanced MLR responses. Suppression by activated spleen cells was not due to cytotoxic effects nor to altered kinetics of the proliferative response. Studies of splenic suppressor cell generation in vivo revealed peak activity four days after alloantigen stimulation with no activity demonstrable at 7 days or at later times. Suppressor cell activity was abrogated by treatment with anti-θC3H serum and complement, and was not alloantigen specific.

“…During the course of tumor allograft rejection in mice, the distribution in sedimentation velocity of splenic CTL changes with time, suggesting that a transition from large to small CTL may occur (7)(8)(9). Since CTL could be detected for several weeks in MLC under appropriate culture conditions (13), it was of interest to investigate the physical properties of CTL induced in vitro.…”

Section: Methodsmentioning

confidence: 99%

Generation of Cytotoxic T Lymphocytes in Vitro

MacDonald

Cerottini

Brunner

1974

The cell-mediated immune response to primary allogeneic stimulation is characterized by the appearance of cytotoxic T lymphocytes (CTL) 1 (see reference 1 for review). Recently, the existence of anamnestic CTL responses to allografts has been suggested by studies in which the ability of normal and alloimmune spleen cells to respond to relevant alloantigens both in vivo (2, 3) and in vitro (4) was quantitatively compared. In other studies, physical characterization of CTL in the spleens of mice undergoing tumor allograft rejection revealed significant differences in size and density between effector cells detected early or late after immunization (5-9), the former being predominantly large and of low density, whereas the latter were mainly small and dense. In view of these observations, two important questions regarding the differentiation and ultimate fate of CTL can be raised: (a) Do the changes in physical properties of CTL with time reflect the differentiation of a single cell lineage, or alternatively the parallel development of several cell lineages? (b) Are the cells capable of mounting an anamnestic response to alloantigens derived from CTL, or are CTL truly end cells capable of no further differentiation?Until individual CTL can be identified and isolated, no definitive answer to these questions is possible. However, with the concomitant development of in vitro systems for the generation of CTL (10-12) and quantitative assays for the estimation of their relative frequency (1, 12), indirect approaches to the study of the differentiation and fate of CTL are now feasible. In a previous paper of this series (13), we presented evidence that an anamnestic response to alloantigens could be demonstrated in long-term mixed leukocyte cultures (MLC). In this