Enhanced suppression of blastogenic responses by weanling mouse lymphoid cells treated with tetrahydrocannabinol in vitro

The suppressive effects of delta 9-tetrahydrocannabinol (THC) on the proliferation of lymphocytes from the spleen, lymph node, and thymus of weanling animals vs adult animals to the T-cell mitogen PHA were examined. THC had a suppressive effect on thymus cells from animals of both younger and older mice. THC suppressed spleen and lymph node cells responses to phytohemagglutinin (PHA) more readily when the cells were obtained from young mice rather than older animals. Suppression by THC in the adult mice was greater in an organ containing fewer mature T lymphocytes such as the thymus in comparison to lymphocytes in secondary organs such as the spleen and lymph nodes which contain more mature lymphocytes.     

The role of the thymus in maturational development of phytohemagglutinin and pokeweed mitogen responsiveness

A sensitive culture system for measuring lymphocyte transformation under physiological conditions by thymidine incorporation into DNA has been developed to study mouse and chick cell responses to mitogens. Both phytohemagglutinin (PHA) and pokeweed mitogen (PWM) stimulated thymus and spleen lymphocytes. Reduced but definite responses were obtained with lymph nodes, but negligible response with bone marrow cells.Thymocytes of newborn mice did not respond to PHA, but responded well to PWM. PHA responsiveness of thymocytes increased with aging until 12 weeks of postnatal life and then decreased in older animals. The level of background thymidine incorporation increased with advancing age. Spleen cells of 2-week-old mice were transformed by PHA and PWM, but in contrast to mouse thymus there was no decrease in older animals.Neonatal thymectomy of mice reduced the response of spleen cells to both PHA and PWM, especially in younger animals. The reduction was almost complete in the case of the PHA response, but only partial with the PWM response. Spleen cells from bursectomised chickens, checked for absence of B cell function, still responded well to both PWM and PHA.The results suggest PHA is a marker for T-lymphocytes in a certain “mature” stage of differentiation. PWM appears to stimulate a wider spectrum of cells.     

In vitro responses of rat lymphocytes following adult thymectomy. II. Increased inhibition by splenic adherent cells of responses to phytohemagglutinin

Adult thymectomy in rats results in a marked fall of spleen cell responsiveness to PHA over a period of days to weeks. Examination of dose-response curves showed that, with high PHA dose or ≥ 10⁶ cells/ml, there is a profound inhibition of the response with spleen cells from thymectomized animals compared with cells of matched sham-operated controls. However, when adherent cells are removed from the cell suspensions, the remaining nonadherent cells give an almost linear dose-response relationship with increasing PHA similar to that exhibited by the nonadherent cells of the controls or sometimes a slightly decreased response. Similarly, when increasing numbers of spleen cells from these animals are cultured (with admixed thymocytes to make a constant total of 2 × 10⁶ cells/ml) with PHA, the linear portion of the doseresponse curve can be extrapolated to give a similar value for the maximal potential response, which again is the same as or somewhat less than the corresponding value for sham-operated controls. A difference in inhibitory capacity is also shown in mixtures of the two spleen cell populations with LNC or with purified spleen cells. It is concluded that adult thymectomy results in increased “suppressor” activity in the spleen within a few days and may reduce slightly the number of T lymphocytes in the spleen reactive with PHA.     

Human lymphocyte responses are enhanced by culture at 40 degrees C.

In vitro responses of human peripheral blood lymphocytes (PBL) were found to be markedly enhanced by culture at 40 degrees C rather than at the conventional temperature of 37 degrees C. We studied proliferative responses of lymphocytes by activation by phytohemagglutinin (PHA) concanavalin A (Con A), pokeweed mitogen (PWM), and allogeneic lymphocytes in mixed lymphocyte culture (MLC) and found enhancement of DNA synthesis at the higher temperature. Cytotoxic T cell responses to allogeneic cells were also enhanced when MLC was done at 40 degrees C. These enhanced immune responses appear to be due in part to increased numbers of participating cells. If in vitro lymphocyte responses correlate with in vivo responses, then fever associated with infection or tumor may be beneficial whereas that associated with autoimmune disorders may have a detrimental effect.     

Phenotypic and Functional Characterization of Lymphocytes from Different Age Groups of Bolivian Squirrel Monkeys (Saimiri boliviensis boliviensis)

Due to many physiological and genetic characteristic similarities to humans, squirrel monkeys provide an ideal animal model specifically for studying malaria, and transmissible spongiform encephalopathies (Creutzfeldt-Jacob disease). While squirrel monkeys three years and older are generally considered adult subjects suitable for use in medical research studies, little is known about the functional properties of lymphocytes in relation to the age of these animals, which could significantly impact the quality and quantity of innate and adaptive immune responses. In this study, we investigated differences in the phenotype and function of lymphocytes subsets of young (3–4 years), adult (8–10 years) and aged (16–19 years) squirrel monkeys. In general, animals in all three age groups exhibited comparable numbers of different lymphocyte subsets except for CD20+ B cells that were significantly lower in aged relative to young animals and T cells subsets expressing both CD4 and CD8 (double positive) were significantly higher in aged relative to young animals. With increasing age, phenotypic differences in central and effector memory T cells subsets were observed, that were more pronounced for the CD8+ T cells. Despite equal proportions of CD3+ T cells among the three age groups, responses of peripheral blood mononuclear cells to T cell mitogens PHA and Con A showed lower IFN-γ producing cells in the aged group than that in the young group. Furthermore, aged animals showed significantly higher plasma levels of inflammatory cytokines IL-6, IFN-γ, TNF-α, IL-10 and IL-12. These findings suggest that while the squirrel monkeys in general share phenotypic and functional similarities of lymphocyte subsets with humans in relation to age, specific differences exist in immune function of lymphocytes between young and old animals that could potentially impact experimental outcomes for which the measurement of immunologic endpoints are critical.     

Effects of immunotherapy and chemotherapy on immunocompetence. A study of patients with acute myeloblastic leukemia in remission

Summary The immunocompetence of 33 patients with acute myeloblastic leukemia in remission and treated with cytostatics (CT) was studied. In addition to cytostatics some of the patients were given immunotherapy (CT+IT).In an attempt to demonstrate immunization against allogeneic leukemic blast cells (or their extracts) or immunostimulation after immunotherapy or, alternatively, immunodepression after maintenance chemotherapy without immunotherapy, delayed hypersensitivity tests and lymphocyte stimulation tests were performed. In most cases PHA seemed to be a stronger stimulator than allogeneic lymphocytes and these seemed to be stronger than allogeneic blasts, although no difference was statisically significant.No significant differences were found in vitro or in vivo between the reactions of CT and CT+IT patients or their lymphocytes to allogeneic myeloblasts or to allogeneic lymphocytes. However, numerically, in vitro and in vivo CT+IT patients reacted more to myeloblasts, CT patients more to lymphocytes. This could suggest antigens on leukemic myeloblasts that are not found on lymphocytes. With present methods we could demonstrate neither immunodepression in patients given only chemotherapy nor nonspecific immunostimulation after immunotherapy. There was no significant difference between the two treatment groups in lymphocyte reactivity against PHA and allogeneic lymphocytes. Nor was the lymphocyte reactivity different from that in a group of healthy persons.Decreasing lymphocyte reactivity to PHA and allogeneic lymphocytes seemed to herald relapse.     

Allogeneic chimerism in scid mice after neonatal transfer of bone marrow.

Allogeneic chimeras are valuable tools for studies of complex immune cell interactions in vivo. Mice with severe combined immune deficiency (scid) should be ideal hosts for chimerism with allogeneic bone marrow cells as these animals lack mature T and B lymphocytes capable of reacting against donor alloantigens. However, it has been difficult to achieve full reconstitution of adult scid mice even using coisogenic bone marrow grafts without prior irradiation of the recipient. We explored ways to generate complete reconstitution of scid mice with allogeneic bone marrow. Unirradiated adult scid recipients of allogeneic bone marrow were only marginally reconstituted. Adult scid mice pretreated with 250 R were reconstituted with allogeneic bone marrow as measured by serum IgM concentration, peripheral lymphoid cellularity, and mitogen responses, but a potentially important immunologic deficit was found in these mice: 250 R caused a 70% loss of scid macrophages and dendritic cells which persisted at least 5 months. By contrast, when scid mice were injected i.p. with allogeneic bone marrow within the first 24 h after birth, rapid and complete reconstitution of both T and B cell lineages was achieved, and the animals had APC that were both donor and host in origin. Considering the extent and duration of engraftment (43 wk) by allogeneic cells in neonatally transplanted scid mice, it was anticipated that their bone marrow would be chimeric. However, the bone marrow contained very few donor-derived cells, suggesting that lymphopoiesis may be taking place in other organs in these chimeras.     

The role of cytostasis in antitumor immunity: comparison between syngeneic and allogeneic systems

Different aspects of the immune response differ with respect to sensitivity of neonatal thymectomy (NTx). The effect of thymectomy on Days 1 and 7 after birth (NTx-1, NTx-7) on antitumor immune responses to both a syngeneic and an allogeneic tumor graft was examined. The tumor used was the same, Meth A fibrosarcoma of BALB/c origin, but the mice inoculated differed. The results show that the immune response to a syngeneic tumor graft is primarily cytostatic rather than cytolytic and is relatively insensitive to neonatal thymectomy, while the response to a large dose of allogeneic tumor cells includes a cytolytic mechanism of high thymus dependence.     

Response of human fetal lymphocytes in xenogeneic mixed leukocyte culture: Phylogenetic and ontogenetic aspects

Cells from liver, thymus, and spleen of human fetuses at different stages of development were capable of a proliferation response against xenogeneic and allogeneic lymphocytes. The kinetics of fetal responses against rat lymphocytes were identical to those of fetal and adult responses against allogeneic cells. With all of the cell types studied, including adult lymphocytes, allogeneic responses were stronger than xenogeneic. Xenogeneic responses against lymphocytes from rat, mouse, or sheep were stronger than those against lymphocytes from rabbit, chicken, snake, or frog. These results are interpreted to indicate that recognition of foreign lymphocytes by human lymphocytes depends on the phylogenetic position of the species used as a source of stimulating cells. The degree of recognition decreases as the phylogenetic distance increases. Specific elimination of responding cells and restimulation with another cell population was used to study the specificity of proliferation responses against mouse and rat lymphocytes. Responses by prethymic liver cells from human fetuses were not due to the existence of specifically recognizing subpopulations. Thymus and spleen at 16 weeks' gestation contained specific subpopulations capable of differentiating between xenogeneic and allogeneic cells, as well as between xenogeneic cells with different intraspecies histocompatibility patterns. Generation of receptor diversity on T lymphocytes is discussed briefly in the light of these findings.     

Cell-cell cooperation in lymphocyte colony formation: studies in human allogeneic marrow transplantation

The pace of restoration of phytohemagglutinin- (PHA) stimulated lymphocyte colony-forming response was investigated in 50 bone marrow transplant (BMT) recipients (49 allogeneic, 1 syngeneic) studied on 86 occasions. On the majority of occasions (28 of 48), patients studied early (3 to 8 wk) after BMT failed to make detectable lymphocyte colonies, whereas patients studied late (greater than 6 mo) after BMT displayed responses comparable to those of healthy adult volunteers. The sequential study of 10 of the 15 patients with positive lymphocyte colony-forming responses early after BMT revealed that this response is short-lived. The results of recipient donor mixing experiments and experiments involving the addition of the lymphokine interleukin 2 (IL 2) to recipient cells indicated that lymphocytes obtained from unresponsive recipients evaluated early after BMT can be driven to colony formation, and suggest that the major limiting component in such subjects is functional T help.     

Demonstration of significant differences in the proliferative capacity of lymphocytes from normal human subjects

Lymphocytes were obtained from six normal human subjects on three to five occasions. Lymphocyte response to pokeweed mitogen (PWM), phytohemagglutinin (PHA), and a pool of allogeneic lymphocytes was measured by incorporation of [³H]thymidine in cultures established in flat- and round-bottom multiwell plates. Unstimulated and mitogen-stimulated thymidine incorporation were not correlated. Therefore, incremental counts rather than stimulation indices were used to express data. Individual lymphocyte responses were more reproducible in round-bottom well plates. Using these data, correlation was found between the responses to PWM and PHA. Neither of these responses was correlated with the mixed lymphocyte reaction. There were no significant differences in the responses of these subjects to allogeneic lymphocytes. This response may, therefore, allow clear distinction between normal and abnormal lymphocyte reactivity. Among these normal subjects significant differences were found in their responses to both PWM and PHA. The biological import of these differences is not known.     

PHA-T cells in systemic lupus erythematosus and in rheumatoid arthritis: abnormalities in HLA class II antigen induction and in autologous mixed lymphocyte reactions

Analysis of T cells from patients with systemic lupus erythematosus (SLE) and with rheumatoid arthritis (RA) identified a deficit in the induction of HLA Class II antigens by PHA although the proliferative response was normal and in the [3H]thymidine incorporation in autologous mixed lymphocyte reactions (MLR) with PHA-T cells as stimulators. In RA these abnormalities were more marked in patients with active disease than in those in clinical remission. The deficit of autologous MLR with PHA-T cells was more marked than that of autologous MLR with non-T cells and of allogeneic MLR. Serum from patients with SLE and with RA did not display any detectable inhibitory activity on the induction of HLA Class II antigens by PHA, on the proliferative response of lymphocytes to PHA, on autologous MLR with PHA-T cells and with non-T cells as stimulators and on allogeneic MLR. These results suggest that the abnormalities we have identified reflect an intrinsic defect of T cells.     

Differential cytotoxicity of activated lymphocytes on allogeneic and xenogeneic target cells. II. Activation by phytohemagglutinin

In the preceding paper it has been shown that human or mouse lymphocytes stimulated by a variety of agents, damaged allogeneic target cells while damage of xenogeneic target cells was weak or absent. In this study, the species specificity of the cytotoxicity of PHA activated lymphocytes has been studied in greater detail. Effector cells were purified lymphocytes either from human peripheral blood, or from spleen or lymph nodes of inbred mice. Target cells were ⁵¹Cr-labeled human Chang liver cells or mouse L cells.PHA stimulated human or mouse lymphocytes were significantly more cytotoxic to allogeneic than to xenogeneic target cells. At low PHA doses at which damage of allogeneic target cells was significant, damage of xenogeneic target cells was very weak or absent. At higher PHA doses, damage of xenogeneic target cells became also significant but always remained at a lower level than that of allogeneic target cells.Prestimulation of human lymphocytes with PHA for 3 days increased their cytotoxic efficiency. Furthermore, damage of human Chang cells by human lymphocytes had a dose-response relationship similar to that valid for stimulation of DNA synthesis. However, damage of mouse L cells by human lymphocytes increased at PHA-doses at which stimulation of DNA-synthesis declined. For mouse lymphocytes, these doseresponse relationships were less clear-cut, probably due to differences in origin and survival of the effector cells. This confirms previous observations that cytotoxicity and DNA-synthesis are different but probably interdependent expressions of lymphocyte activation.     

The mitogenic response of cryopreserved human lymphocytes in a microculture system

Fresh blood lymphocytes from nine health donors have been compared with samples from the same donors, recovered after period of 2 to 21 months storage in liquid nitrogen, for the capacity to respond to a range of mitogens in vitro. A microculture assay was used, requireing aliquots of only 25,000 cells. The mean levels of 14C-thymidine uptake for fresh and frozen samples were closely comparable when the cells had been stimulated by PHA, Pokeweed or mitomycin-C-treated allogeneic lymphoblastoid cells. Lymphocytes from six East African donors, frozen by a very simple technique, were recovered after 3 or more years storage in liquid nitrogen. Five of the samples were in good condition as judged by cell viability and the capacity to form spontaneous 'E' rosettes with sheep erythrocytes. These five samples also responded extremely well to PHA, PWM and mitomycin-C-treated allogeneic lymphoblastoid cells using the microculture assay. This study extends the range of applications of cell banks in which small aliquots of blood lymphocytes are stored in liquid nitrogen for periods of several years.     

Proliferation of peripheral lymphocytes to interleukin-2 and interleukin-4 after marrow transplantation.

Defects in the interleukin-2 (IL-2)-mediated T-lymphocyte activation/proliferation pathway have been implicated as contributing to the compromised immune function observed in patients following bone marrow transplantation (BMT). Since interleukin-4 (IL-4) is also involved in T-lymphocyte function, we have examined whether phytohemagglutinin (PHA)- or anti-CD3 (OKT3)-activated lymphocytes obtained from patients after allogeneic or autologous BMT are capable of proliferating in response to human recombinant IL-4, and compared these results to those obtained using human recombinant IL-2. Peripheral blood lymphocytes from marrow graft recipients were initially cultured for 3 days in the presence of PHA or OKT3. Such mitogen-activated lymphocytes exhibited little or no proliferation (as assessed by incorporation of [3H]-thymidine) following culture for an additional 3 days in the presence of IL-4 or IL-2. Results were similar for lymphocytes obtained from patients early (less than 4 months) after marrow grafting and those obtained from long-term marrow graft recipients with chronic graft-vs-host disease at the time of testing. In contrast, lymphocytes obtained from healthy individuals proliferated in response to IL-4, as well as to IL-2, following initial activation with PHA or OKT3. Immunofluorescence analysis showed that in normals equal numbers of CD4 and CD8 cells proliferated after stimulation with anti-CD3 antibody and IL-2. However, in BMT patients there was a predominant proliferation of CD8 cells using the same stimulator. These results indicate that defects in the IL-4-mediated T-lymphocyte activation/proliferation pathway may also contribute to the immunodeficiency observed following BMT.     

Lymphocytes in thymomas are tolerant to self-MHC.

Neoplastic epithelial cells of thymoma apparently retain the function of the cortical epithelial cells of normal thymus because a large number of nonneoplastic T cells in thymomas are often CD4+8+. However, the lack of medullary structure suggests that thymomas may lack some of the function of the normal thymus, especially the function of the medullary interdigitating cells to induce tolerance to self-antigens on T cells. Thymoma is often associated with autoimmune diseases, most frequently, myasthenia gravis. This suggests that the microenvironment of a thymoma may not be able to induce T cell tolerance to self-antigens. We addressed this question by testing the lymphocytes in thymomas for proliferative responses to mitogens and allogeneic or autologous stimulator cells. The lymphocytes in thymomas proliferated consistently in response to PHA and to allogeneic cells even when the response to OKT3 was undetectable. However, neither the thymoma lymphocytes nor the peripheral blood lymphocytes in these patients proliferated in response to autologous cells.     

Immunomodulating activity of p-hydroxyphenyllactic and ascorbic acids

p-Hydroxyphenyl lactic acid (PHA) in a concentration of 5 . 10(-5) M produced a significant inhibition of cell proliferation in response to alloantigens in a one-way mixed lymphocyte culture (MLC) in colonic cancer patients and in blast transformation in response to suboptimal doses of Con A. Multiple administration of ascorbic acid in an optimal concentration to the culture increased the proliferative response of lymphocytes to alloantigens and Con A. PHA and ascorbic acid did not exhibit any immunomodulating action during the use of healthy donors' lymphocytes or lymphocytes from colonic cancer patients, transformed with optimal mitogen doses. PHA did not affect the production of cytotoxic T lymphocytes in the MLC of the spleens of allogeneic mice but inhibited lymphocyte proliferation in response to alloantigens in the MLC of the spleens obtained from B6 and vitamin A deficient animals.     

On the lifespan of virgin T lymphocytes.

To study the lifespan of virgin T lymphocytes, we removed the thymus from adult female mice and then, at various times afterward, tested their ability to mount an immune response to a newly encountered Ag, the male Ag H-Y. We found that unprimed thymectomized mice were able to generate a primary response to H-Y for some time after thymectomy but lost this ability at approximately 6 mo. In contrast, mice that were primed to H-Y just after thymectomy continued to display immunological memory to H-Y for >1 year. These experiments show that primary immune responses disappear in the absence of a thymus.     

Mixed lymphocyte reaction in mice genetically selected for high (Hi/PHA) or low (Lo/PHA) responsiveness to phytohemagglutinin.

Lymph node cells from Hi/PHA and Lo/PHA mice were evaluated for proliferative response after stimulation by allogeneic lymphocytes (MLR) originating from four inbred strains of different H-2 haplotype (C57B1/6, DBA/2, CBA, A). Reactivity to MLR and PHA were compared in these two lines and in the four inbred strains. The high and low responder status of Hi/PHA and Lo/PHA, as determined by T mitogens lymphocyte responsiveness, was also observed when one measured T responsiveness after MLR. Values obtained with the four inbred strains are included in the range of those measured in Hi/PHA and Lo/PHA cells when stimulated by PHA as well as by allogeneic cells. In contrast, when used as stimulator cells, Hi/PHA or Lo/PHA lymphocytes induce an equivalent proliferative response versus every responder inbred strain studied. These experiments support the hypothesis of a common genetic control of proliferative response following PHA or MLR stimulation. The genes implicated would be different from those coding for I region associated antigens.     

Alloantigen-induced T helper activity. I. Minimal genetic differences necessary to induce a positive allogeneic effect.

Addition of histoincompatible lymphocytes can influence the course of ongoing immune responses. Such allogeneic effects may either augment or diminish immune responses. We describe here the minimal genetic differences necessary to generate positive allogeneic effects (allohelp) in a humoral immune response. The antibody response to sheep erythrocytes of T cell-depleted mouse spleen cells was reconstituted by addition of syngeneic or allogeneic nylon wool column-passaged spleen T cells. T cells were pretreated with mitomycin C before culture to prevent development of allo-suppression and cytotoxic lymphocytes. Positive allogeneic effects were operationally defined as superior helper effects (to generate greater antibody forming cell responses) with T cells allogeneic rather than syngeneic to the responding B cells. Thus, addition of allogeneic T cells resulted in many more antibody forming cells than did equal numbers of syngeneic T cells, and fewer allogeneic than syngeneic T cells were necessary to generate comparable responses. With congenic, recombinant, and mutant mouse lines, genetic differences in the H-2 complex and those associated with Mls were each sufficient to provide positive allogeneic effects. With intra-H-2 recombinants, differences at either I or D were sufficient. A disparity at H-2K alone, as provided by the H-2 mutant B6.C-H-2ba against the parental line C57BL/6By, also induced helper effects. The significance of these results is discussed.