The role of macrophages in stimulation of immune induction and myelopoiesis: II: analysis of genetic restriction involved in the stimulation of granulocyte colony precursors or mature lymphocytes using factors prepared from different recombinant inbred strains of mice

The genetic restriction involved in the reconstitution of immune responses in macrophage-depleted mouse spleen cultures, or the induction of colony formation in bone marrow cultures, by different molecular-weight species of lymphostimulatory molecules derived from mouse peritoneal cell suspensions is reported. The data suggest little evidence for genetic restriction in the ability of any of the factors to stimulate bone marrow colony formation in vitro. However, when immunological stimulation was investigated, a restriction coded for by genes in the K/D end of the MHC (70-90K factor) or in the I region of the MHC (30-45K factor) was observed. A third species of lymphostimulatory molecule (15K) showed no such restriction. Further evidence is presented to suggest that the active moiety in the 70-90K molecule(s) is a 15K-like species (nonrestricted in its ability to reconstitute cells from different strains of mice.

The role of macrophages in stimulation of immune induction and myelopoiesis. I: Comparison of activity of macrophage-derived factors in granulopoiesis and immunostimulation

Hemopoietic growth and immunological inductive factors from human peripheral leukocyte conditioned medium and mouse macrophage culture supernatant fluids were compared. Factors derived from human peripheral leukocyte conditioned medium were found to substitute for those of mouse macrophage derivation in immunological assays, namely, induction of a cytotoxic T-lymphocyte response in macrophage-depleted mouse spleen cultures. Association of macrophage-derived factors with B2-microglobulin (B2m) antigen determinants was observed by inhibition with great antihuman B2m, affinity chromatography, and direct replacement of mouse macrophage-derived factors with human urinary B2m.

Effect of gold sodium thiomalate on murine lymphocyte functions

The in vitro effects of gold sodium thiomalate (GTM) on various murine splenic lymphocytic functions were tested. The presence of GTM in cultures of splenic cells suppressed anti-hapten responses to both thymus-independent and thymus-dependent antigens. GTM also suppressed the in vitro generation of cytotoxic effector cells as well as the mitogenic response to both T cell and B cell mitogens. This suppression could not be reversed by the addition of irradiated spleen cells. Spleen cells exposed to GTM for 4 hr prior to culture also exhibited similarly suppressed functions, although their functional capacity could be fully restored by the addition of irradiated spleen cells. These results show that GTM inhibits both humoral and cellular immune mechanisms and appears to act primarily at the accessory (macrophage) cell level, with perhaps a secondary effect on T lymphocytes.

Suppression of cytotoxic response to histoincompatible cells. II. Analysis of the role of two independent T suppressor pools in maintenance of neonatally induced allograft tolerance in mice

The kinetics of appearance of the precursors of SuppA cells (capable of inhibiting CTLp leads to CTL) or SuppB cells (capable of inhibiting (stem cells leads to CTLp) in neonatal mice, as well as the appearance of SuppA/SuppB cells in mice given neonatal innoculations of semiallogeneic spleen cells has been investigated. The data obtained are consistent with the idea that SuppA cells have a natural role to play in the induction of neonatal tolerance, whereas SuppB cells may be more important for the maintenance of the tolerant state. Unlike the level of SuppB cells, the level of SuppA cells in tolerant mice seems to be modulated by the presence of the tolerizing determinants. Data are provided to show that SuppB cells, once induced in tolerant mice, can adoptively transfer specific allograft unresponsiveness to newborn syngeneic mice in the absence of added tolerizing antigen, whereas SuppA cells are not able to do so. These data fit the notion that SuppB cells may be responsible for the phenotype of clonal deletion.

Suppression of Cytotoxic Response to Histoincompatible Cells

Spleen and thymus cell populations from normal or allograft tolerant mice have been cultured for 5 days with specific alloantigens and examined for their reactivity in three assay systems. No consistent correlation was observed between the production of cytotoxic T cells (CTL) in these cultures and the ability of such cultured cells to inhibit specifically a CML response from fresh normal spleen cells directed to the priming alloantigens. Furthermore, suppressor cells measured in this latter assay were apparently distinct from those able to inhibit the production of cytotoxic lymphocyte precursors (CTLp) from bone marrow stem cells in lethally irradiated bone marrow protected mice. Velocity sedimentation experiments confirmed that both the precursor and effector cells for the two suppressor systems were physically separable, and were distinct from CTLp or CTL, respectively. Precursor cells for the two suppressor systems investigated belong to the short-lived cortical thymus cell population.

Suppression of Cytotoxic Response to Histoincompatible Cells

The kinetics of appearance of the precursors of SuppA cells (capable of inhibiting CTLp → CTL) or SuppB cells (capable of inhibiting (stem cells → CTLp) in neonatal mice, as well as the appearance of SuppA/SuppB cells in mice given neonatal innoculations of semiallogeneic spleen cells has been investigated. The data obtained are consistent with the idea that SuppA cells have a natural role to play in the induction of neonatal tolerance, whereas SuppB cells may be more important for the maintenance of the tolerant state. Unlike the level of SuppB cells, the level of SuppA cells in tolerant mice seems to be modulated by the presence of the tolerizing determinants. Data are provided to show that SuppB cells, once induced in tolerant mice, can adoptively transfer specific allograft unresponsiveness to newborn syngeneic mice in the absence of added tolerizing antigen, whereas SuppA cells are not able to do so. These data fit the notion that SuppB cells may be responsible for the phenotype of clonal deletion.

Suppression of cytotoxic response to histoincompatible cells. I. Evidence for two types of T lymphocyte-derived suppressors acting at different stages in the induction of a cytotoxic response

Spleen and thymus cell populations from normal or allograft tolerant mice have been cultured for 5 days with specific alloantigens and examined for their reactivity in three assay systems. No consistent correlation was observed between the production of cytotoxic T cells (CTL) in these cultures and the ability of such cultured cells to inhibit specifically a CML response from fresh normal spleen cells directed to the priming alloantigens. Furthermore, suppressor cells measured in this latter assay were apparently distinct from those able to inhibit the production of cytotoxic lymphocyte precursors (CTLp) from bone marrow stem cells in lethally irradiated bone marrow protected mice. Velocity sedimentation experiments confirmed that both the precursor and effector cells for the two suppressor systems were physically separable, and were distinct from CTLp or CTL, respectively. Precursor cells for the two suppressor systems investigated belong to the short-lived cortical thymus cell population.

Requirement for matching T cell and B cell subsets in secondary anti-hapten antibody responses

The in vitro secondary anti-hapten response to trinitrophenylated keyhole limpet hemocyanin (TNP-KLH) has been investigated using B and T cells from the same or a pool of identically primed syngeneic individuals. The optimum antibody response obtained from B cells of any given animal was seen when the same individual's T cells were used as a helper cell source. This individual preference was lost if secondary challenge in culture was made with TNP on a heterologous carrier, with the helper cells obtained from suitably primed individuals or a pool thereof. These data are interpreted in terms of a network theory for the regulation of immune responses under physiological conditions.

Response of tumour-related and normal lymphocytes to antigens on fibroblasts from embryos of varying age

The in vitro cytotoxic immune response of spleen lymphocytes from primiparous and tumour-related mice to embryonic cells from embryos of varying age and tumour cells has been investigated. The results indicate that lymphocytes from both primiparous and tumour-related (i.e., tumour-bearing or tumour-excised) animals give a response which is greater than that from cells from control mice ("virgin cells"). Moreover, in this putative anamnestic response the immune cells detect antigenic differences in the cell populations of embryos of varying age, which are not as readily demonstrable when cytotoxicity is derived from virgin cells. As a further indication of the in vivo priming to embryo-assoicated antigens, the data show that the precursors of cytotoxic cells apparently undergo a blastogenic response in the presence of embryo antigen, and revert to small quiescent cells when antigen is removed, in a way entirely analogous to that described for reactivity of mixed leucocyte cultures to antigens of the major histocompatibility complex. Finally, it seems that in animals immediately after removal of embryonic antigen (and to a lesser degree in virgin or late-embryo-immune mice) there exists a suppressor cell population which inhibits an anti-embryo cytotoxic response far more than an antiallograft response.

Differentiation of functionally active mouse T-lymphocytes from functionally inactive bone marrow precursors

An investigation has been made of the development of various T cell functions in lethally irradiated mice reconstituted with anti-0 treated spleen or bone marrow cells. Evidence is presented to show that both organs contain a post-thymic precursor pool able to regenerate by 15 days limited T cell responses in thymectomized recipients. A prethymic pool also exists in each organ able to regenerate, at a later date, first a suppressor T cell population and probably later, mature functional T cells involved in helper functions and cell mediated lympholysis. The spleen is apparently a better source of precursors of the suppressor cells than bone marrow, while a poorer source of precursors of the other T cell functions. All T cell functions investigated apparently first appear in large cells which undergo a reversion to small cells without necessarily maturing to their full potential reactivity. By following the kinetics of appearance of T cell functions, and the physical parameters of the cells with which these functions are associated, it is shown that PHA responding and Con A responding cells, cytotoxic T cell progenitors, helper T cells for antibody production and helper T cells for cytotoxicity induction can all at some stage of differentiation be separated from one another.

Role of macrophage-derived factors in generation of cytotoxic and antibody responses

The ability of macrophage subpopulations, separated by virtue of differences in size, to liberate soluble factors able to reconstitute antibody and cell-mediated immune responses in macrophage-depleted lymphoid cultures has been investigated. Evidence is presented to show that all macrophages release trypsin- and pepsin-sensitive molecules with molecular weights of 30,000 to 35,000 and 50,000 to 70,000 that are able to reconstitute only syngeneic lymphocyte responses. In contrast, a molecule(s) with molecular weight of 10,000 to 15,000 daltons is released only by large macrophages and can apparently reconstitute both syngeneic and allogeneic lymphocyte responses. This material is also pepsin-sensitive and, to a lesser degree, trypsin-sensitive.

Heteroantisera prepared against B lymphocytes at different stages of differentiation. I. Preparation of sera and cytotoxicity to lymphoid cells from different organs

A routine method is described whereby anti-mouse B-cell antisera can be raised in rabbits. As judged by trypan blue dye exclusion these sera have negligible cytotoxicity to murine T lymphocytes but seem to detect differences in non-T lymphocytes in different organs. By sedimentation analysis some of the sera may detect (in addition to mature B cells) earlier precursors of mature B lymphocytes in bone marrow and spleen.

Heteroantisera prepared against B lymphocytes at different stages of differentiation. II. Functional analysis of cytotoxicity to different B-cell populations

Functional studies on heteroantisera raised against mouse B cells in rabbits suggest a correlation between thymus-independent B cells and LPS-responsive B cells, and differences in either from thymus-dependent B cells. Furthermore it seems possible to follow B-lymphocyte differentiation from antigen-uncommitted precursors to antigen committed immature B cells to mature B lymphocytes by the loss and acquisition of surface markers distinguished by these heteroantisera. Additional evidence is provided that there are distinctive antigenic differences between antibody forming cells raised from the same B-cell source after in vivo or in vitro immunization.

Autoreactivity developing spontaneously in cultured mouse spleen cells. III. Inhibition of anti-embryo cytotoxicity in male T lymphocytes by female non-T cells

Cultured female spleen cells develop less cytotoxicity to embryo-associated antigens than do cultured male spleen cells. This difference is less pronounced if the cells are treated before culture with a specific hetero-anti-B cell antiserum. Female non-T cells (especially from primiparous animals) can decrease the spontaneously developing T-cell cytotoxicity in male splenic T lymphocytes upon culture. By artificially manipulating the T cell: non-T cell ratio in the spleen population prior to culture, it seems one can alter the type of cytotoxic mechanism (to embryo-associated antigens) which develops in the cultures.

Autoreactivity developing spontaneously in cultured mouse spleen cells. I. Evidence that cytotoxicity is directed against embryo-associated antigen

We have investigated the ability of male-mouse spleen cells before and after culture in the absence of deliberate antigenic stimulation to show specific cytotoxicity to syngeneic embryo-fibroblast cells. The data suggest that cytotoxicity which develops spontaneously in such spleen cell cultures is directed primarily against embryo-associated antigens. Syngeneic Con-A-stimulated spleen cells, which, unlike fresh normal spleen cells, are also lysed by rabbit anti-mouse embryo antisera, are also a suitable target to demonstrate spontaneously developing cytotoxicity.

Control of the immune response: role of macrophages in regulation of antibody-and cell-mediated immune responses

The ability of peritoneal macrophage subpopulations, separated into different classes according to their size, to reconstitute antibody or cellular immune responses in macrophage-depleted spleen cells has been investigated. Data are presented to show that whether reconstitution is by "normal" or "activated" macrophages, be they syngeneic or allogeneic to the lymphocyte source, different populations reconstitute antibody and cellular immunity. Reconstitution is in general by two classes of macrophages, small and large. The former seem to reconstitute only if syngeneic to the responding lymphocyte pool, whereas large macrophages reconstitute immune responses from allogeneic lymphocytes as well as syngeneic lymphocytes. Evidence is also presented to show that syngeneic large macrophages can determine the type of immune response reconstituted; that is, with greater numbers of large cells only cytotoxic responses (and not T-dependent antibody formation) were reconstituted and vice versa.

Immunity to murine sarcoma virus induced tumours. IV. Direct cellular cytolysis of 51Cr labelled target cells in vitro and analysis of blocking factors which modulate cytotoxicity

The antigen specific cell mediated cytotoxicity of MSV immune spleen lymphocytes to 51Cr labelled murine lymphoma cells was wholly abolished by pretreatment of the spleen cells with anti-theta antibody and complement. Early during the immune response to MSV the cytotoxic acitivity was inhibited by incubation of immune lymphocytes with "late progressor" or "early regressor" serum. Immune lymphocytes at later times were more refractory to such inhibition by serum blocking factors. Although unfractionated cytotoxic lymphocytes, irrespective of the time after MSV infection at which they were tested, were inhibited by soluble tumour associated antigen (TAA), a subpopulation of cytotoxic T cells was identified which was inhibited neither by antigen nor serum.

Cell-mediated immunity to Moloney sarcoma virus in mice. II. Analysis of antigenic specificities involved in T lymphocyte-mediated in vivo rejection of murine sarcoma virus-induced tumors

Sublethally irradiated BALB/c mice innoculated with Moloney sarcoma virus (MSVm) develop progressively growing tumors and die within 30 days of virus innoculation. These animals can be protected from tumor progression (and death) by innoculation of small numbers of MSV-immune T lymphocytes from MSV-M innoculated (but unirradiated) animals. T lymphocytes in these donor animals have been shown to express immunity to a variety of viral and virally-induced antigens. We have investigated whether immunity to any one of these antigens was critically important in leading to protection of the irradiated animals by sensitizing normal T lymphocytes in vitro to different viral antigens and examining the ability of these sensitized cells to protect the irradiated recipients. Data is presented to show that cells sensitized in vitro to MSV-transformed fibroblasts, and to purified antigens with group specificity, but not to viral envelope antigens, or whole virus, are capable of protecting the irradiated MS innoculated animals.