The effect of heterologous anti-lymphocyte seerum on mouse hemopoietic stem cells

Crossreaction of antilymphocyte globulin with human granulocyte colony-forming cells

Clinical preparations of horse antilymphocyteglobulin (ALG) were found to inhibit human bone marrow granulocyte colony growth. This effect was enhanced by complement and was dose dependent, being almost complete at ALG concentrations of 100 microgram/ml. Inhibition was a property of ALG but not of normal horse globulin. However, short incubation of ALG with bone marrow cells occasionally stimulated colony growth and normal horse globulin regularly stimulated it. Three hours' incubation of bone marrow cells with ALG was needed to produce consistent colony inhibition, which was measurable as a reduction in the expected number of colonies and as a fall in the colony: cluster ratio of surviving cell aggregates. Absorption of ALG on acute myeloid leukaemia blast cells removed the inhibiting property of the ALG while preserving its lymphocytotoxic action. Serum from two patients receiving ALG treatment inhibited colony growth for up to 48 hours after ALG administration. The results suggest the presence in ALG of antibodies specifically cytotoxic to myeloid stem cells which may relate to its myleosuppressive properties in vivo, and also indicate that it should be possible to remove antimyeloid antibodies from ALG by absorption. The use of such purified ALG would have advantages in clinical bone marrow transplantation.

The significance of lymphocytosis in congenital hypoplastic anemia

Two infants with congenital hypoplastic anemia had an unusual number of lymphocytes in their peripheral blood and in the bone marrow. This caused an erroneous diagnosis of acute lymphocytic leukemia to be made in the first case and inappropriate therapy to be administered for three months. The second of these cases provided an unusual opportunity to study human erythrocyte precursor dynamics. Serial bone marrow aspirates, obtained after institution of treatment with a corticosteroid, revealed an initial increase in labeled lymphocytes, a concomitant decrease in their number, and the subsequent appearance of erythroid elements. These findings suggest that cells classified morphologically as lymphocytes may serve as erythroid precursors in human beings.

Studies on the distribution of macrophages derived from rat bone marrow cells in xenogeneic radiation chimaeras

Lethally-irradiated mice were injected with rat bone marrow cells and examined subsequently for the presence of rat macrophages, using an indirect fluorescent antibody test in conjunction with a fluorochrome-labelled phagocytic cell marker. Donor bone marrow cells were fractionated by (1) adherence, (2) magnetic removal of phagocytic cells containing ingested carbonyl iron and (3) treatment with lymphocyte-absorbed anti-rat macrophage serum either in vitro or in vivo. Extensive rat cell proliferation occurred in the resulting xenogeneic chimaeras by or after Day 4 and increased during the next week. The precursor of both the free and fixed macrophages was contained in the non-adherent, non-phagocytic population of bone marrow cells. The anti-macrophage serum was not selective and abolished the capability of bone marrow cells to proliferate.

Cytology and histology of haemopoietic cell transplantation under the influence of antilymphocyte serum (ALS) in mice. I. The in vivo effect of antilymphocytic globulin on haemopoietic tissue

C57BL/6J mice were treated with ALS, ALG, normal rabbit serum (NRS) or IgG of the rabbit for a period of 6 days. To study the xenogeneic antigenicity of ALG and its antilymphocytic effect separately, half the mice were made tolerant to IgG of the rabbit. While a short schedule of injections of ultracentrifuged IgG induced tolerance to IgG, this tolerance was eliminated by the subsequent treatment with ALG. A prolonged injection schedule over 44 days did, however, lead to a tolerance which persisted after ALG treatment. [¹³¹I]IgG elimination proved to be a more sensitive control of tolerance than immunodiffusion.

Semiquantitative cytology revealed a decline in lymphocytes, erythroblasts and megakaryocytes in the bone marrow and erythroblastosis and megakaryocytosis in the spleen. Cells of the myeloid series invariably increased in number. The effect on erythroblasts persisted after removal of contaminating haemagglutinins. ALG-treated animals intolerant to IgG had about four times more splenic plasma cells than ALG-treated mice tolerant to IgG. The 6 days' treatment with ALS reduced the absolute number of nucleated bone marrow cells by 16% and doubled the spleen indices. Under this treatment, relative and absolute cell counts revealed an ALG-induced shift of erythroblasts, megakaryocytes and perhaps also of plasma cells from the bone marrow to the spleen. The effect of NRS or IgG was similar to that of ALS or ALG but remained on a lower level.

The remarkable changes in the histologic structure of the splenic follicles after ALG treatment were almost completely reversed by a prior induction of tolerance to IgG.

Cytology and histology of haemopoietic cell transplantation under the influence of ALS in mice. II. The effect of marrow from donors pretreated with antilymphocyte serum (ALS) on the recipient

Cytology and histology of recipients of allogeneic bone marrow were studied 13. 20, 24, 30 and 34 days after transplantation. The developing chronic secondary disease was characterized by increased numbers of myeloid cells, by lymphopenia and by erythroblastopenia in the bone marrow and the spleen. Erythroblastopenia together with lymphopenia and augmented myeloid cells also occurred in irradiated F₁-hybrids suffering from a chronic homologous disease. The latter model eliminated the following as a cause of erythroblastopenia in secondary disease: (1) host-versus-graft reaction against donor-type erythroblasts for immunogenetical reasons, and (2) graft-versus-host reaction against recipient-type erythroblasts since they had already been destroyed by irradiation. Treatment of the donor with ALS resulted in a suppression of homologous disease in F₁-hybrids with a cytology resembling that of recipients of syngeneic spleen cells. The same treatment only delayed the onset of chronic secondary disease in recipients of allogeneic bone marrow. These allogeneic recipients, in contrast to the F₁-hybrid recipients, died with the typical morphology of a chronic secondary disease.

In recipients of syngeneic bone marrow from donors treated with ALS, repopulation with lymphocytes was somewhat delayed and transient erythroblastosis in the spleen occurred 20 days after transplantation.

Depletion of long-lived lymphocytes in old New Zealand black mice

Labelling studies with tritiated thymidine in NZB mice revealed that old mice of this strain with established Coombs positive haemolytic anaemia were depleted predominantly of long-lived small lymphocytes. Lymphopoiesis in the bonemarrow was relatively less affected suggesting that the peripheral destruction or deviation of re-circulating lymphocytes and not a precursor cell deficiency may account for the depletion of these cells. Old NZB mice in which the development of Coombs positive haemolytic anaemia, but not other disease features, has been prevented by thymectomy and treatment with anti-lymphocyte globulin several months earlier were equally deficient in this population of lymphocytes. C57BL mice, subjected to the same regime largely regenerated this population during the subsequent 12 months and rejected skin homografts in the same time as young controls of the same strain. Loss of lymphocytes responsible for antigen recognition would account for the impaired cellular immunity of old NZB mice observed in this study and described earlier by other authors. This process appears to accompany the progression of the spontaneous disease in this strain.

The effect of anti-lymphocytic IgG on unsensitized and sensitized spleen cells in vivo and in vitro

Rat spleen cells sensitized to bovine serum albumin and treated in vitro with anti-lymphocytic IgG are unable to transfer secondary immunological (humoral) responsiveness to irradiated isogeneic rats. Similar in vitro treatment of unsensitized spleen cells has a significant, though less marked effect, upon their ability to confer primary humoral responsiveness to irradiated recipients.