Nazareth Gengozian

Thymus specificity in lethally irradiated mice treated with rat bone marrow.

Summary Immunologic and cytologic tests indicate that the thymuses of lethally irradiated mice protected with rat bone marrow are repopulated by rat-type cells. The agglutination tests showed this repopulation of the thymus by donor cells to be 100% complete 30 days after treatment, and the cytologic analysis of dividing cells showed 100% rat-type cells 21 days after treatment. Although the histologic architecture of these thymuses was often normal, recovery of the thymuses in terms of weight was incomplete.

Suppression of humoral and cell-mediated immune responses in vitro by benzo(a)pyrene.

The effect of benzo(a)pyrene (BaP) at different molar (M) concentrations on the in vitro anti-sheep red blood cell (SRBC) plaque (antibody) forming cell (PFC) response and the one-way mixed lymphocyte response (MLR) was tested. Inhibition of the PFC response and the MLR occurred when spleen cells were exposed to a wide range of BaP concentrations from 10(-4) M to 10(-8) M. Maximum depression of the responses occurred at 10(-5) M for PFC production (47% of controls) and for the MLR (19% of controls) as measured by a stimulation index. No significant loss in cell viability was observed at this or lower molar concentrations of BaP. The non-carcinogenic analog of BaP, benzo(e)pyrene, did not suppress PFC responses at comparable concentrations. This in vitro system will facilitate manipulations of T and B lymphocytes and macrophages (adherent cells) in a controlled culture environment for precisely characterizing the sensitivity of these cells and their subpopulations on exposure to BaP.

Depression of the Primary Immune Response by dl-Penicillamine.

Summary Treatment of mice with dipenicillamine for 3 weeks before antigen injection resulted in an overall reduction in antibody formation while treatment immediately after antigen injection for 8 consecutive days had no effect. In those groups showing depression of antibody response, the formation of both the 19S and 7S antibody was reduced, the latter type also showing a delay in appearance but subsequently reaching levels comparable to those seen in normal animals. Administration of penicillamine intravenously to animals having only 19S antibody in the serum resulted in an immediate but transient reduction of antibody titer. This observation, along with that showing failure of penicillamine to affect the formation of both 19S and 7S antibody when given after antigen injection, suggests that the depressive effect is primarily at the cellular level of the immunologic process rather than through an intravascular dissociation process.

ABNORMAL IMMUNE MECHANISM IN ALLOGENEIC RADIATION CHIMERAS.

Mice were subjected to x-rays (950 roentgens) and injected with isogeneic (isologous) or allogeneic (homnologous) bone marrow. Six to 8 months later these chimeras were injected with Salmonella typhi flagellar antigen, and the formation of antibodies resistant and sensitive to destruction by treatment in vitro with 2-mercaptoethanol was determined. The allogeneic chimeras showed almost normal amounts of serumn antibody after a third injection of antigen but a relative defect in their ability to synthesize antibody resistant to 2-mercaptoethanol. Apparently control of antibody formation becomes abnormal in the presence of the immunologic tolerance existing between the host and the foreign hematopoietic graft.

Transplantation of Rat Bone Marrow in Irradiated Mice: Effect of Exposure Rate

Mice were irradiated at several different exposure rates so that they received a total of 900 roentgens over the whole body. Within 2 hours they were injected with rat bone marrow. The success of the transplantation depended upon the rate at which the animals had been irradiated: the higher the rate, the greater the success of the grafts. Failure of grafts in mice subjected to low exposure-rates was associated with antibody formation. The data indicate existence of an immune mechanism which is dependent on the radiation exposure-rate.

Erythrocyte-rosetting properties of feline blood lymphocytes and their relationship to monoclonal antibodies to T lymphocytes.

Rosette formation of feline peripheral blood leukocytes with guinea pig (GP) and gerbil (G) erythrocytes (E) has been shown in an earlier study to identify T lymphocytes expressing helper and suppressor cell activity, respectively. This T lymphocyte distinction was based on the removal of the E-rosetting populations from peripheral blood leukocytes (PBL) and the subsequent functional evaluation of the remaining cells in a pokeweed mitogen (PWM)-induced synthesis of immunoglobulin (Ig). In the present study, we demonstrate a direct helper and suppressor function of GPE- and GE-rosetted cells, respectively, wherein the induction of Ig synthesis is altered in a positive or negative way by the addition of the cells to a control target population. A pan-T monoclonal antibody (mAb), CT843, and mAbs to the CD4 (CT248) and CD8 (CT87) subsets are also described; their specificities are established in functional assays, the PWM-induced Ig synthesis and the production of interleukin-2 following Concanavalin A stimulation of PBL, and a biochemical analysis of the surface membrane antigens detected by the mAbs. Immunopreclpitation and SDS-PAGE analyses showed CT248 to react with a ~60-kDa protein under both reducing and nonreducing conditions. Under reducing conditions, CT87 reacted with one subunit at ~35 kDa; a second faint band at ~39 kDa was poorly resolved. mAb CT843 detected a heterodimer of ~70 and ~60 kDa under both reducing and nonreducing conditions. The relationship of the mAbs to E-rosetting was examined in FACScan analyses and rosette Inhibition studies. The percentage of GE-rosetting cells agreed with the percentage of cells stained with the CD8 mAb, whereas a comparison of GPE-rosetting and staining with the CD4 mAb showed variability. The binding of GE to PBL was blocked by pretreatment of PBL with the CD8 mAb, whereas no inhibition of GPE rosettes was observed with any of the mAbs. In a previous study, we had shown that an overnight culture of feline PBL at 37°C leads to the development of a second population of GPE-rosetting cells, also having a helper function. The relationship of the two GPE-rosetting populations to the CD4 mAb, CT248, was examined in rosette depletion studies and FACScan analyses. It was found that depletion of the GPE-rosetting cells from fresh, i.e., Day 0 cells, removed only a small percentage of cells reactive with the CD4 mAb, whereas GPE-rosette depletions performed on Day 1 PBL, which contained both populations of GPE-rosetting cells, removed almost all cells reactive with this antibody. The latter study suggests that the GPE-rosetting phenomenon is detecting two subsets of CD4 cells with T helper function, those present in fresh blood and those acquiring the GPE receptor after an overnight culture.

Demonstration of an early host-graft incompatibility reaction in radiation chimeras with the Jerne plaque technique.

Summary The Jerne plaque technique was used to demonstrate the presence of an early immunologic reaction between host and donor tissues in lethally irradiated mice treated with rat or hamster bone marrow. Evidence for both host and graft activity was obtained from spleen cells of mice that had been treated with hamster bone marrow. The responses obtained were of low magnitude and variable, and were evident primarily through the first 6 days post-treatment. A cause and effect relationship of this early immune reaction to the etiology of secondary disease in foreign marrow radiation chimeras is suggested.

Transplantation in the Marmoset (Callithricidae): A Technique for Orthotopic, Fitted Skin Grafts

Summary The marmoset, a small New World primate, Callithricidae, is known to be naturally endowed with blood-cell chimerism. The high frequency of fraternal twinning with placental vascular anastomosis between young in this family explains this consistent mosaicism. This unique feature suggests hematopoietic tolerance. In anticipation of skin allograft studies to demonstrate immunologic tolerance between twin marmosets, skin autografts were attempted. A successful technique for fitted skin grafts to the chest emerged from the consideration of hair-growth phase, graft size and site, surgical anesthesia, control of infection, and mechanical protection. Of a series of 50 consecutive autografts reported, 48 survived.