Role of the H-2 complex in the homing affinity of injected lymphoid cells to the host's lymph nodes

Analysis of the genetic control of lymphocyte positioning

A possible role for the major histocompatibility complex (MHC) in the localization of lymphocytes in different lymphoid organs was investigated using inbred mouse strains. Lymphocytes labelled with the intracellular fluorochrome Hoechst 33342 (H33342) were transfused intravenously (IV) into unimmunized mice and the distribution of these labelled lymphocytes examined. In some combinations (e.g. C57BL/6----CBA) 2 h after injection allogeneic lymphocytes accumulated in the region between the marginal zones and outer aspects of the white pulp of the spleen. In contrast, in syngeneic controls (e.g. CBA----CBA) the lymphocytes migrated normally into the while pulp. Similar results were obtained in Peyer's patches. Mapping studies in the spleen indicated that the failure to migrate normally is predominantly controlled by the MHC complex, although some non-MHC genes may play a role. In the case of the MHC the most definitive combination was BALB/c-H-2dm2 (H-2L deletion mutant) lymphocytes transfused into BALB/c recipients, the mutant lymphocytes failing to migrate normally and, therefore, implicating the H-2L region in the phenomenon. No differences in the viability of labelled lymphocytes at 6 and 24 h after injection into either syngeneic or allogeneic recipients suggests that the inability of cells to passage through lymphoid organs may represent inappropriate receptors rather than elimination of the allogeneic lymphocytes by natural killer cells (NK) as previously proposed.

A genetic analysis of natural resistance to nonsyngeneic cells: the role of H-2

The genetic control of natural resistance in vivo to four natural killer (NK) cell-resistant H-2 homozygous lymphoid tumor cell lines was investigated by following the survival and organ distribution of cells prelabeled with radioactive iododeoxyuridine. Backcross mice derived from DBA/2J and CBA/J parents were injected with H-2d tumor cells and tumor cell elimination was lowest in H-2d homozygotes. Natural killer cell activity was also reduced in mice with the H-2d haplotype, but no direct correlation between NK cell levels against YAC-1 or SL2-5 lymphoma cells and natural resistance in vivo was demonstrable. Analysis of 23 BXD recombinant inbred strains indicated that natural resistance to H-2d tumors was restricted to H-2b strains. There was no direct association of NK cell activity with H-2 type in the BXD strains and NK cell levels did not correlate with tumor survival in vivo. By comparing natural resistance to H-2d and H-2b tumors in DBA/2, C57BL/6, B6D2F1, and B10.D2 mice we found that H-2 nonidentity between the tumor and the host, rather than the host H-2 haplotype, determined whether natural resistance occurred. Again, NK cell activity against YAC-1 cells was not predictive of tumor survival in these strains. These results provide genetic evidence that NK cells alone cannot account for natural resistance to H-2 nonidentical cells of hemopoietic origin.

The rapid elimination of allogeneic lymphocytes: relationship to established mechanisms of immunity and to lymphocyte traffic

Allogeneic lymphocyte cytotoxicity (ALC) refers to the destruction of lymphocyte beginning within a few hours of intravenous injection into non-sensitized, allogeneic recipients. Usually this has been detected in rats and mice by comparing the localization of 51Cr-labelled lymphocytes in the tissues of allogeneic and syngeneic recipients. In a particular strain combination the existence of ALC is supported by deficient localization of allogeneic lymphocytes in the LN, lungs and blood mononuclear population and an excess of the label that had been associated with allogeneic cells in the lymph plasma, blood plasma and kidneys. As the destruction of the allogeneic cells occurs in the lymphatic tissues, especially the spleen, it is paradoxical that there is sometimes an excess of the label associated with allogeneic cells in the spleen but evidence is presented that most of the isotope is no longer associated with living cells in that organ at 24 h after transfer. The data cannot be explained by an altered distribution of allogeneic lymphocytes between different organs. Experiments on the early migration of lymphocytes from the blood of syngeneic and allogeneic recipients point unequivocally to the conclusion that the adhesion of lymphocytes to specialized vascular endothelium in LN and their consequent entry into LN does not require that the lymphocytes and the endothelial cells share MHC products. The characteristics of ALC stressed in this review include the following: 1) it is independent of T-cell activation, either of host T-cells or of donor T-cells: 2) B- and T-cells are about equally vulnerable to ALC; 3) it varies greatly between different strain combinations regardless of other indices of cellular and humoral immunity; 4) F1 hybrid donor cells are vulnerable but the effect is always less marked than with allogeneic cells; 5) ALC is less radio-sensitive than primary cellular or humoral immune responses; 6) adoptive transfer of ALC can be achieved with TDL from nude rats. The possible mechanism underlying ALC has been debated in terms of natural killer cells recognizing certain allo-antigens or alternatively pre-existing "natural" antibody with low affinity for allogeneic cells leading to their elimination by ADCC. The argument hinges on the necessity for antibody and cannot be resolved by current data.

Natural cytotoxicity: early killing of allogeneic lymphocytes in rats

In many strain combinations among inbred rats, intravenously injected 51Cr-labelled lymphocytes are destroyed in substantial numbers by unsensitized allogeneic hosts. Destruction of cells (referred to as natural cytotoxicity (NC)) occurs within a few hours of injection, and is characterised by a decreased accumulation of radioactivity in the lymph nodes and increased renal excretion of label by allogeneic hosts, as compared with the distribution of label in syngeneic recipients of the same cell suspension. An intact spleen is necessary for killing. The level of NC expressed is consistent for a given donor-host combination. Using arbitrary criteria to compare the levels of NC expressed by different donor-host combinations among inbred rats, 13 of 95 strain combinations have been shown to express high NC, 63 intermediate NC and 19 low NC. The level of NC expressed cannot be correlated with the extent to which donor and host differ in respect of known MHC genes. Segregation analysis has shown high NC to be controlled by at least 2 independently segregating genes, one of which is MHC-linked. It is possible to weaken or abrogate NC by the neonatal injection of bone-marrow cells from the donor strain, and to reverse this reduced reactivity by the injection of host strain lymphocytes. The substitution of either the donor (P1) or the host (P2) by the P1 X P2)F1 hybrid reduces or eliminates NC in strain combinations normally expressing high NC. It is currently uncertain whether NC can be augmented. In the single strain combination in which maturation has been studied, NC becomes evident during the 4th week of life and attains adult levels during the 6th-7th weeks. NC is at least partially radio-sensitive. Two groups of reactivities appear to be related to NC: (i) those which have been identified in the context of aberrant lymphocyte homing, and for which allogeneic lymphocytes are the targets; (ii) the group of natural resistance systems which includes NK cells, and whose reactivity is directed against a variety of other target cells.

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

In some strain combinations among inbred rats 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 leads to 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.

In vivo elimination of allogeneic lymphocytes in normal and T-cell-deficient rats. Elimination does not require T cells

The distribution of allogeneic and syngeneic thoracic duct lymphocytes was studied over 24 h in normal and T-cell-deficient animals (thymectomized, irradiated rats, 'B rats', or congenitally athymic nude rats). Initial migration from blood was no less for allogenic than for syngeneic cells. After 24 h, however, a marked deficit of radioactively labelled allogeneic cells as compared with syngeneic cells was found in the lymphoid tissue, whereas the allogeneic isotope was recovered in a relatively greater amount in liver, kidneys, and cell-free plasma and lymph. Most of the allogeneic cells are evidently destroyed within the first 24 h and their isotope released into body fluids. Our studies also revealed this process to be even more evident in T-cell-depleted environments. Autoradiographic studies of recipient nude rat spleens showed that allogeneic cells were not found in the great number seen in syngeneic transfers, but a high grain density in the periarteriolar lymphocyte sheath area could be observed. Granula seemed to be predominantly located over large nonlymphoid cells. The elimination of allogeneic lymphocytes is therefore governed by mechanisms independent of an intact thymus and may be due to a cell population or factor more active in nude animals than in their non-nude littermates.

Maintenance of allogeneic cell recognition in allograft tolerant mice

The organ distribution of 51Cr-labelled lymph node cells following transfer to syngeneic, allogeneic and specifically tolerant allogeneic recipients were compared. Neonatal induction of transplantation tolerance in several donor-recipient combinations involving different H-2 haplotypes had no effect on the reduction of homing into lymph nodes and the values of the homing did not differ from those of the untreated allogeneic recipients. In both cases, they amounted to 45-55% of the syngeneic controls. Even those neonatally treated animals, which had not been rendered tolerant at birth and rejected test skin grafts, were not capable of removing the transferred allogeneic cells by a typical immune elimination. The results indicate that animals recognize allogeneic cells, irrespective of whether or not they reject test skin grafts.

H-2D antigens released by thymocytes and cell adhesion

The identity and complete purification of mouse Thymocyte Interaction Modulation Factor (T IMF) is described. Use of silver-stained PAGE methods shows that previous methods of purification yield preparations containing two protein or glycoprotein bands. T IMF activity from H-2k mice can be bound to 15.5.5 monoclonal antibody columns (anti H-2 Dk) but not to 11.4.1 columns (anti H-2 Kk). The activity can be recovered from 15.5.5 columns and runs on PAGE aa a single band at approximately 34,000 Daltons. This evidence together with previous evidence relating the activity to H-2D locus argues that T IMF is a soluble H-2 D antigen fragment equivalent to a papainized H-2 fragment. Additional evidence is presented on an improved method of assay of T IMF activity, on its inactivation by enzymes and serine-esterase inhibitors and of its effect on syngeneic leucocytes and macrophages. It is shown that T IMF is not appreciably toxic cells.