Natural cytotoxicity in rats: Radiation-induced changes in the early killing of allogeneic cells

In some strain combinations among inbred tats intravenously injected ⁵¹Cr-labeled lymphocytes are rapidly destroyed in substantial numbers by unsensitized allogeneic hosts. This phenomenon has been referred to as natural cytotoxicity (NC) and is characterized by decreased lymph node radioactivity, increased kidney and urine radioactivity, and to a lesser extent increased liver radioactivity in allogeneic hosts, when compared with the distribution of label in syngeneic recipients of the same cell suspension. A single exposure to 800 rad either 1 or 7 days before the injection of ⁵¹Cr-labeled lymphocytes effected a reduction in NC as defined by all the above parameters in a strain combination exhibiting high NC. The same dosage of radiation abolished NC in a strain combination exhibiting intermediate → low NC. Because NC was not always completely abolished, the phenomenon was held to be partially radiosensitive. An increased accumulation of ⁵¹Cr-labeled lymphocytes was seen in the lymph nodes of both syngeneic and allogeneic irradiated hosts when compared with nonirradiated controls, although the increase was greater in allogeneic than in syngeneic hosts. This increased colonization in the lymph nodes of irradiated hosts seemed unlikely to be due to an increase in the available “space” in the lymph nodes following irradiation.     

Radiation-induced alterations in murine lymphocyte homing patterns: I. Radiolabeling studies

In vitro X-irradiation of ⁵¹Cr-labeled spleen, lymph node, bone marrow, or thymus cells was found to alter their subsequent in vivo distribution significantly in syngeneic BDF₁ mice. Irradiated cells demonstrated an increased distribution to the liver and a significantly lower retention in the lungs. Cells going to the lymph nodes or Peyer's patches showed a significant exposure-dependent decrease in homing following irradiation. Irradiated lymph node cells homed in greater numbers to the spleen and bone marrow, while irradiated cells from other sources showed no preferential distribution to the same tissues. Sampling host tissues at various times after irradiation and injection did not demonstrate any return to normal patterns of distribution. The alterations in lymphocyte homing observed after in vitro irradiation appear to be due to the elimination of a selective population of lymphocytes or membrane alterations of viable cells, and the detection of these homing changes is in turn dependent upon the relative numbers of various lymphoid subpopulations which are obtained from different cell sources. Radiation-induced alterations in the normal homing patterns of lymphoid cells may thus be of considerable importance in the evaluation of subsequent functional assays in recipient animals.     

Further evidence for the existence of B-lymphocyte subpopulations.

We have studied the homing properties of B lymphocytes by using ⁵¹Cr-labeled lymphoid cells obtained from athymic, nu/nu mice, and animals made T-lymphocyte deficient by thymectomy and lethal irradiation followed by reconstitution with syngeneic bone marrow. Comparison was made to the patterns of distribution observed when cell preparations containing normal numbers of T and B lymphocytes were migrated. A small but significant percentage of labeled lymphocytes from lymph nodes, spleen, Peyer's Patches, and bone marrow of T-cell-deficient animals was shown to be lymph node seeking. Secondary transfers of lymph node cells from primary recipients caused enrichment of this lymph node-seeking population. Treatment of T-lymphocyte-deficient lymphoid cell preparations with neuraminidase reduced the percentages of cells homing to the lymph nodes. The data showed that B lymphocytes exhibit unique homing properties when injected into normal recipients. In addition, direct comparison of the homing patterns of B lymphocytes prepared from spleen and lymph nodes of athymic mice revealed differences suggesting that these lymphoid organs contained unique mixtures of at least two different kinds of B cell. The evidence supports the notion that the B-lymphocyte populations contain at least two subpopulations, one of which possesses the ability to home to lymph nodes.     

Changes in the homing properties of labeled lymphoid cells caused by solid tumor growth

The effect of a progressively growing fibrosarcoma upon the distribution of ⁵¹Cr-labeled cells from the lymph nodes, spleen, thymus, bone marrow and Peyer's Patches was measured in tumor-bearing recipient mice. Tumor presence caused a uniform depression of migration of labeled cells to the bone marrow. In most cases increased homing of cells to the spleen was also observed. Labeled cells prepared from lymph nodes and Peyer's Patches were generally unaffected by the presence of a growing tumor. Migration of labeled cells from tumor bearing donors into normal syngeneic recipients suggests depletion or incapacitation of parts of the T-cell population of the spleen. These results emphasize the important relationship between splenic function and tumor progression.     

Virus-induced alterations of lymphoid tissue. IV. The effect of Newcastle disease virus on the fate of transfused thoracic duct lymphocytes

⁵¹Cr-labeled thoracic duct lymphocytes were briefly incubated at 4 °C with Newcastle disease virus (NDV) and then infused into syngeneic rats. Virus diverted the homing of many donor cells from lymph nodes and spleen to the liver. Evidence was obtained suggesting that some NDV-treated lymphocytes initially trapped in the liver subsequently migrated into the lymph nodes. The results imply that NDV transiently interrupts the normal route of lymphocyte migration. Alterations in lymphocyte distribution were mediated by attachment of virus to the cell surface and were the same as those induced by incubating lymphocytes with V. cholera neuraminidase before infusion. It appears that reactions involving 2–3′ and/or2–8′ linked sialyl residues on the surface of recirculating lymphocytes can markedly affect their distribution in the body.     

Control mechanism of lymphocyte traffic. A study of the action of two sulfated polysaccharides on the distribution of 51Cr- and [3H]adenosine-labeled mouse lymph node cells

The effects of dextrans of varying molecular weights and of pentosan sulfate on the distribution of ⁵¹Cr-labeled mouse lymph node cells were studied in vivo, i.e., in recipients treated with the sulfated polysaccharides, and in vitro, i.e., by following the fate of cells treated in vitro, in intact syngeneic recipients. Both types of experiments demonstrate that dextrans, especially dextran sulfate (DXS) and pentosan sulfate (PS), considerably reduce lymph node entry of lymphocytes, with concomitant increases in the blood and, in the case of DXS, in both the blood and lungs. A parallel quantitative autoradiographic analysis of the distribution of [³H]adenosine-labeled cells confirmed the data with the ⁵¹Cr-labeled cells and, in adidtion, indicated that DXS and PS slow down circulation of lymphocytes through the marginal zone and red pulp of the spleen and, in the case of DXS, in the pulmonary capillary bed. Unusually large numbers of unlabeled lymphocytes were found in the endothelial wall of the post-capillary venules in lymph nodes of PS-treated mice.     

RNA in the periphery of rapidly proliferating mouse lymphoid cells

RNA in the peripheries of various populations of lymph node cells (LNC) has been evaluated by measuring the electrophoretic mobilities of cells, before and after treatment with active or inactivated ribonucleases. Three different populations of LNC were studied: (1) “resting” normal age control LNC; (2) “syngeneic” LNC from irradiated (C3H × C57BL)F₁ or C3H mice four to six days following transplantation of syngeneic spleen cells; such cells were progeny of lymphopoietic progenitor cells of the spleen; and (3) “allogeneic” LNC from irradiated (C3H × C57BL)F₁ mice four to six days after grafting C3H (parental) spleen cells; such cells were progeny of lymphopoietic progenitor cells, but also alloantigen-sensitive cells of the spleen which proliferate in response to the host's alloantigens (a “graft-versus-host” immunological reaction). Whereas the normal LNC had no detectable peripheral RNA, the allogeneic and syngeneic LNC did, i.e., ribonuclease reduced their mean electrophoretic mobilities by 13.6 and 9.2 per cent, respectively. Since both allogeneic and syngeneic LNC had peripheral RNA, no specific correlation could be made with immunological activity. ³H-uridine and ¹⁴C-thymidine incorporation into lymph nodes was greatest in allogeneic, intermediate in syngeneic and least in age control lymph nodes, indicating a “population shift” in the spleen cell chimeras toward relatively immature, rapidly proliferating cells, which had a relatively high rate of RNA synthesis. Thus, rapidly proliferating lymphoid cells do have RNA in their peripheries, but its relation to specific immunological function has yet to be ascertained.     

Effect of tumor immunity on the distribution of labeled lymphoid cells in tumor-challenged mice

The distribution of ⁵¹Cr-labeled lymphoid cells from normal mice and mice immunized against a tumor were compared after intravenous inoculation of the labeled cells into normal syngeneic recipients. Spleen cell preparations from immune donors contained increased percentages of spleen and bone marrow-seeking cells, thus suggesting expansion of these cell populations when immunity to a tumor exists. Homing of labeled normal cells in tumor cell-injected normal animals was somewhat different from that seen in tumor cell-inoculated mice that were immunized against the tumor. In the latter case, accumulations of lymph node and spleen cells in recipient lymph nodes and bone marrow were consistently lower. In contrast, lymphoid cells from animals immunized against the tumor were found to accumulate in virtually the same percentages in lymphoid organs of normal and immune recipients. The behavior of lymphoid cell populations from thymus or bone marrow that consist mainly of precursor cells was unaffected by presence of malignancy and/or tumor immunity.     

Effects of concanavalin A on the migration of radioactively labeled lymphoid cells

The effects of the jackbean globulin Concanaalin A (Con A) on the distribution of radioactive ⁵¹Cr-labeled lymph node cells was studied in CBA mice. Lymph node cells treated in vitro with Con A in subagglutinating noncytotoxic doses were unable to “home” to the lymph nodes of syngeneic recipients after intraenous injection. The effect was almost immediate and seemed unrelated to mitogenesis. The inhibitory effect of Con A on lymphocyte migration could be partially reersed by alpha-methyl mannoside; the degree of migratory impairment was related to the amount of Con A bound to the lymphocyte surface at the time of transfer. The membrane site at which Con A binds to the lymphocytes is similar to that which is bound by heterologous antilymphocyte serum but is probably distinct from the theta antigenic site. These data lend support to the hypothesis that surface lymphocyte carbohydrate determinants are involved in the specific lymphocyte “homing” receptor.     

The influence of strong transplantation antigens (Ag-B) on lymphocyte migration in vivo.

The tissue localization of syngeneic thoracic duct lymphocytes was compared to that of allogeneic cells in four rat strain combinations differing at the Ag-B locus (HO → DA, DA → HO, AO → HO, HO → AO). Dual isotope labeling with [³H]uridine and [¹⁴C]uridine was applied in order so that the distribution of allogeneic and syngeneic cells could be followed in one recipient. During the first couple of hours after iv injection, allogeneic lymphocytes usually migrated as easily into the various tissues as did syngeneic cells. However, after 24 and 48 hr, a reduced amount of label associated with allogeneic cells was often measured in the tissues. This reduction differed in magnitude in the different strain combinations and was most pronounced in the lymph nodes. A reduced number of allogeneic cells also appeared in the thoracic duct. By contrast, no reduced localization of allogeneic lymphocytes was measured in the draining popliteal lymph nodes late after sc injection. In preimmunized animals allogeneic cells were rapidly removed from the blood and therefore failed to localize in the lymphoid tissues. Furthermore, the lymph node localization of allogeneic cells was more like that of syngeneic cells in splenectomized rats, as well as in irradiated recipients (when the irradiation was given shortly before cell transfer). It is concluded that transplantation antigens play no essential role in the interaction between recirculating lymphocytes and the venous endothelium at the sites where the large-scale physiological emigration of the cells takes place (the HEVS of the lymph nodes and the marginal zone vessels of the spleen). The elimination of allogeneic cells is found later; it probably takes place in the lymph nodes and spleen. Possible mechanisms responsible for this rapid removal of allogeneic lymphocytes in nonimmunized recipients are discussed.     

Natural cytotoxicity in rats: Strain distribution and genetics

The term natural cytotoxicity (NC) describes a phenomenon in rats whereby significant numbers of intravenously injected ⁵¹Cr-labeled lymph node cells are rapidly destroyed by unsensitized allogeneic hosts. Cell death is reflected in a decreased accumulation of labeled cells in the host lymph nodes, with a corresponding increase in the label excreted by the kidney. Natural cytotoxicity has been studied in 95 allogeneic donor-host combinations among inbred rats and in a segregating population of F1 backcross animals. On the basis of lymphocyte distribution patterns, the individual donor-host combinations have been categorized as exhibiting high NC (13 strain combinations), intermediate NC (63 strain combinations), or low NC (19 strain combinations). Analysis of the segregating F1 backcross population showed NC to be controlled by at least two independently segregating genes, one of which was linked to the MHC, and the other of which was possibly, but by no means certainly, X linked. No linkage was demonstrated with respect to coat color loci (C, A, H) or to kappa chain allotype (RI-1). Natural cytotoxicity appears to belong to a group of several phenomena characterized by the rapid destruction of allogeneic cells by apparently unsensitized hosts.     

Variation in the homing properties of 51Cr-labeled thy antigen-positive lymphoma

The homing properties of five thy antigen-positive murine lymphoma cell lines in normal syngeneic mice were compared to those of thymus, lymph node, bone marrow, and spleen cells. YAC lymphoma cells migrated in significant numbers to the spleen but in somewhat smaller percentages than normal lymphoid cells. An immunoselected subline of YAC was recovered from recipient spleens in about double the amounts observed with the parental lymphoma line. The migration patterns produced by lymphoma YC8, AKR, and LSTRA more closely resemble those of the selected subline of YAC. None of the lymphoma used in this study homed to recipient lymph nodes. That the selective distribution of labeled lymphoma cells was a function of cell viability was demonstrated by the fact that heat-killed lymphoma cells were recovered almost exclusively from the liver. Neuraminidase treatment, prior to ⁵¹Cr labeling, changed the migration in vivo of all the lymphoma studied except YAC. In contrast, trypsinization of the lymphoma did not influence their distribution in vivo. Binding of concanavalin A (Con A) to the cell membrane modified the homing of normal lymph node cells but did not change the migration of lymphoma cells. The conclusion was drawn that many receptors normally present on T lymphocytes are missing or modified after transformation and that the lymphoma in question more closely resembles the sessile splenic T1 lymphocyte.     

Peripheral tolerance induced in lymph nodes by syngeneic spleen cells inhibits generation of CTLs to hapten-altered self antigens but not to alloantigens.

The immunological tolerance that is induced in lymph nodes that have been exposed to syngeneic spleen cells has been examined. Development of cytotoxic T lymphocytes was used to assess the immunological status of the lymph node cells. The tolerance was studied from the viewpoint of its induction, its activation, and its specificity. We had already reported that injecting either T or B cells of splenic origin into a regional lymph node environment a week prior to immunization for CTL to hapten-altered self antigens prevents development of the CTL. Here, we confirm that syngeneic splenic cells but not lymph node cells will induce the suppression provided that spleen cells are not coupled with hapten. We now report that splenic cells that cannot replicate or synthesize and secrete protein are capable of inducing the suppression. The data suggest a preformed surface marker peculiar to spleen cells and perhaps on cells that traverse the thymus induces local tolerance that is mediated by suppressor cells. Triggering the induced suppressor T cells (previously identified as CD8-) was achieved by syngeneic spleen cells as well as by H-2-compatible, Mls-disparate spleen cells but not by syngeneic lymph node cells or apparently by allogeneic spleen cells. Furthermore, triggering suppression was achieved by hapten-coupled syngeneic spleen cells whereas such cells would not induce the suppression. Thus, activating the suppressor cells requires reexposure to splenic cells of the proper MHC haplotype, unaltered or coupled with either TNP or FITC. Once triggered, the suppression was manifested toward CTL generation against hapten-coupled syngeneic antigens on either spleen or lymph node cells but not against allogeneic antigens. Thus, the specificity of the tolerance was directed to altered self antigens despite its induction by unaltered spleen antigen. Furthermore, for suppression to be seen the spleen antigen was not required to be on the hapten-coupled syngeneic cells used for the CTL immunization. The relationship of the splenic cell "antigen" to hapten-altered self antigens and to other surface markers and its site of acquisition within the body and its significance for cell homing have become intriguing questions of importance. This information has been discussed from the viewpoint of its applicability to autoimmune diseases as well as to cessation of inflammatory reactions that may be mediated by lymph node cells.     

Random recirculation of small T lymphocytes from thoracic duct lymph in the mouse

The migration of ⁵¹Cr-labeled nylon-wool separated mouse thoracic duct T cells has been followed in order to determine whether there is a circulation of small (nondividing) T cells through the small intestine. Approximately 6% of the injected dose of T-TDL localized in the small intestine (minus Peyer's patches). Experiments revealed that this gut-localizing cell population consisted almost entirely, if not exclusively, of lymphoblasts present in mouse T-TDL. When lymphoblasts and small lymphocytes from mouse T-TDL were separated by velocity sedimentation, and the migration of separated fractions was studied, we found large cells (66% blasts) migrated well to the gut but poorly to the lymph nodes, whereas small cells (2% blasts) showed minimal migration to the gut but localized randomly in lymph nodes and spleen. The in vivo distribution of small cells from T-TDL was similar to that of T-PLN. Furthermore, the recirculatory patterns of both ⁵¹Cr-labeled T-TDL and T-PLN were found to be identical as accessed by their rate of recovery in the thoracic duct lymph of recipient mice. These results support the notion that the vast majority of T-TDL and T-PLN are part of a common pool of recirculating T cells which recirculate randomly through lymph nodes and spleen and not the small intestine.     

Natural killer cell activity in mouse aggregation chimeras

The activity of natural killer (NK) cells in spleen against syngeneic and allogeneic tumor cells was studied by the use of tetraparental mouse chimeras. Chimeras were produced by aggregation of early embryos of histoincompatible mouse strains of “high” and “low” NK cell activity. NK activities of spleen cells were assayed in vitro by the ⁵¹Cr-release method. Coat color distribution and isozymal analysis (glucose-phosphate isomerase) of several lymphoid organs (thymus, lymph nodes, and bone marrow) revealed a predominant share of the “high”-NK-reactive genotype in the chimeras. However, the cellular NK activity against two target cell lines differing in their susceptibility to lysis was significantly lower in chimeras than in the “high”-reactive strain. Addition of “low”-NK spleen cells or of NH₄Cl-inactivated “high”-NK spleen cells to “high”-NK spleen cells inhibited their cytolytic activity. Possible mechanisms of the suppression of the cytolytic capacity of NK cells in chimeras are discussed.     

Inhibition of erythroid cell growth by allogeneic murine lymphocytes. Evidence for a synergism between lymph node cells and thymocytes

Murine lymphoid cells from thymus and lymph nodes were tested for synergistic response in a graft-vs-host test. The test is based on the principle that allogeneic lymphocytes inhibit erythroid cell proliferation in the spleens of irradiated mice infused with syngeneic bone marrow cells.I was observed that mixtures of thymocytes and lymph node cells from the same parental strain yielded graft-vs-host responses in irradiated F₁-hybrids higher than expected by summing the responses of the two cell populations tested separately. A similar synergistic response was obtained using mixtures of thymocytes and lymph node cells obtained from the two parental strains of the hybrid, whereas such an effect was not detected using mixtures of lymph node cells or mixtures of thymocytes from the two parental strains. Nor could synergy be demonstrated between parental strain lymph node cells and thymocytes syngeneic with the bone marrow target cells. Thymocytes obtained from one parental strain which were injected into its irradiated F₁-hybrid transformed into a population of sensitized cells in the spleens of the recipients. This transformation was suppressed by the simultaneous injection of lymph node cells from the second parental strain. Since there is a synergistic immune response by such cell mixtures it is concluded that thymocytes may enhance the graft-vs-host response of lymph node cells. Parental strain thymocytes and lymph node cells, the latter being specifically immunologically tolerant to the bone marrow target cells, failed to give a synergistic response indicating that thymocytes do not transform unresponsive lymphocytes into responsive, but rather enhance the reactivity of existing, specifically responsive cells.The results thus show that thymocytes may enhance the response of lymph node cells in this specific graft-vs-host assay.     

Enteric migration of radiolabeled lymphocytes.

The migratory patterns of circulating radioisotopically labeled lymphocytes were studied by means of serial transfer into syngeneic recipients. A sub-population of ⁵¹Cr-labeled lymphocytes, defined by their property of additionally labeling with IUDR, was found to possess migrational specificity for the lamina propria of stomach, jejeunum, ileum, and large bowel. This gut-seeking population was found within peripheral nodes, mesenteric nodes, Peyer's patches, thymus, and spleen and consisted of both B and T cells. Labeled lymphocytes homed to intestine during all phases of the cell cycle, suggesting that specificity for the gut is not linked to specific events in the lymphocyte cell cycle.     

Migratory patterns of B lymphocytes. IV. Effect of anti-Ig on follicular localization of radioactively labeled murine spleen and bone marrow cells.

A study was made of the localization of nylon-wool-adherent (AD) and nonadherent (NA) murine spleen cells in lymphoid tissue of irradiated syngeneic recipients. Cells were labeled in vitro with [³H]uridine or ⁵¹Cr and injected intravenously. Localization in recipient tissues was expressed as percent of injected radioactivity. NA and AD [³H]uridine labeled cells gave spleen to lymph node (S:LN) ratios of 1.0 and 2.7, respectively. After treatment of AD cells with rabbit anti-mouse Fab + C at 37 °C, localization in S decreased markedly.NA cells primarily localized in LN paracortex and splenic periarteriolar sheaths. Untreated and NRS-treated AD cells localized in lymphoid follicles, whereas anti-Fab-treated AD cells did not. When ⁵¹Cr-labeled AD cells were treated with anti-Fab at 4 °C without C, there was a transient decrease in splenic localization at 24 hr followed by a recovery to the normal pattern at 48 hr after transfer. [³H]uridine-labeled bone marrow (BM) cells showed less localization in lymphoid tissue than did S cells. Some BM cells were seen in LN follicles, particularly at 48 hr after transfer, but this localization was not affected by prior treatment with anti-Fab + C. The possible role of surface Ig in the determination of follicular localization of B lymphocytes is discussed.     

Influenza A virus interaction with murine lymphocytes. I. The influence of influenza virus A/Japan 305 (H2N2) on the pattern of migration of recirculating lymphocytes.

The effect of influenza virus A/Japan 305 (H2N2) on the path of migration of recirculating lymphocytes has been studied. 51Cr-labeled rat thoracic duct lymphocytes (TDL) were incubated with virus at 37 degrees C for 1 hr and then infused i.v. into syngeneic recipients which were killed 1 hr later. Virus-treated TDL accumulated in the liver and their recovery in lymph nodes and spleen was severely reduced. Changes in lymphocytes induced by virus developed rapidly and were evident after incubation for only 15 min. UV-irradiated virus altered the pattern of lymphocyte localization but attachment of heat-inactivated virus to lymphocytes in vitro had no effect on their distribution in vivo. Evidence was obtained that some virus-treated TDL, initially sequestered in the liver, subsequently recovered their ability to circulate normally. Recovery was not complete and a population of cells failed to regain their ability to home into lymph nodes. Evidence is also presented demonstrating that influenza virus affected the homing properties of both T and B cells. It is suggested that aberrations in lymphocyte homing were mediated by the viral neuraminidase which induces changes in the cell membrane leading to their accumulation in the liver.     

Mechanisms of in vivo generation of cytotoxic activity against allograft: 1. Local differentiation of mature cytotoxic T lymphocytes in rejection of allogeneic lymphocytes

Although cytotoxic activity was not detected within the spleen and regional lymph nodes from mice immunized sc with allogeneic lymphocytes, such activity was detected consistently in glass-nonadherent and anti-θ-sensitive peritoneal exudate cells (PE cells) from Day 5 after immunization and reached a maximum by Day 7. Immunized spleen cells developed cytotoxic T lymphocytes (CTLs) earlier and more effectively than normal spleen cells when transferred ip into X-irradiated syngeneic normal mice together with immunizing antigen, while they did not become cytotoxic when transferred without antigen. These results suggest that spleen and lymph node cells which may have differentiated into some transitional state by in vivo immunization may differentiate into mature CTLs, following direct contact with antigen at the site of graft. CTLs generated there appear to be responsible for the rejection of allogeneic lymphocytes. Cytotoxicity of PE cells was also generated in X-irradiated mice and augmented cytotoxicity was generated by treatment with cyclophosphamide.