Immunological enhancement of rat renal allografts using rabbit antisera with specificity for rat transplantation antigens.

Rabbits immunized with particulate and soluble preparations of rat lymphoid tissue of the HO strain produced antisera which reacted without strain specificity on rat lymphocytes. Absorption of the sera with tissue from the AS strain of rat removed the antibodies reacting with AS tissue leaving activity against HO cells only. Studies with backcross rats showed that the antigens detected by these sera were products of the AgB genes or genes segragating with them. The immunosuppressive activity of rabbit antisera specific for Ag-B5 rat transplantation antigens was tested in a rat renal allograft assay. Some of the antisera markedly prolonged the survival of (AS X HO)F1 kidneys transplanted to AS rats. The prolongation of graft survival was not due to ALS activity since the sera were active in the absence of antibody directed against recipient antigens. There was no correlation between in vivo enhancement and anti-donor lymphocytotoxic titres of the xenoantisera.     

The alloantibody response and active enhancement of some rat renal allografts.

Lewis rats that were given injections of 10(6) to 10(8) (Lewis X Brown Norway) F1 hybrid bone marrow cells produce predominantly, if not exclusively, 19S lymphocytotoxic antibodies. A number of Lewis rats that received transplants of perfused renal allografts from bone marrow donors at, or near, the peak of IgM response survival for well over 200 days with good renal function and no histological evidence of chronic rejection. All long-surviving rats had detectable lymphocytotoxic antibodies up to 120 days after allografting; late enhancing antibodies had the restricted specificity possibly identical or similar to anti-I region antisera. All rats bearing prolonged renal allografts were unable to accept donor-specific skin grafts or to respond with specific lymphocytotoxic antibodies following skin grafting. The possible involvement of non-complement-fixing 19S alloantibodies in active enhancement of rat renal allografts is discussed.     

Active enhancement of rat kidney allografts. Effect of pretreatment with prednisolone and donor-specific antigen.

(Lewis x Brown Norway) F1 hybrid rat kidney allografts were transplanted to bilaterally nephrectomized Lewis recipients pretreated in various ways. The mean survival time of untreated controls was 16.1 +/- 1.7 days. All rats pretreated with 1.67 g/kg of semi-soluble Brown Norway spleen extract and 5 mg/kg of prednisolone on days 15, 8, and 1 before transplantation survived indefinitely. Pretreatment with semi-soluble or soluble extract alone prolonged survival modestly (36.5 +/- 13.6 and 30.8 +/- 5.6 days, respectively), but the former induced indefinite survival in two of eight animals. Prednisolone on its own failed to bring about prolongation of survival and the combined use of soluble extract and prednisolone did not reveal a synergistic effect. Cytotoxic antibody titres in animals showing indefinite survival were very low, and there was no correlation between antibody titres and prolonged survival. It is assumed that the pretreatment with semi-soluble extract and prednisolone inhibited the formation of cytotoxic antibodies as well as cell-mediated immunity, and encouraged the formation of enhancing antibodies. To study the cellular and humoral reactivity of five prolonged survived kidney recipients, 1st and 2nd donor-specific skin grafts were carried out. The humoral and cell-mediated responses were somewhat delayed in these recipients but otherwise normal except for the absence of the second-set phenomenon.     

Effect of azathioprine and prednisolone on passive enhancement of rat renal allografts.

Passive enhancement provides only partial suppression of rejection in the (DA X Lewis)F1 to Lewis renal allograft model. Suboptimal (8 mg/kg/day) and supraoptimal (30 mg/kg/day) doses of azathioprine administered with enhancing serum failed to suppress the rejection reaction in enhanced animals. Similarly, suboptimal (4 mg/kg/day) and optimal (16 mg/kg/day) doses of methylprednisolone were ineffective. However, the onset of rejection in enhanced animals was delayed by the use of both azathioprine (30 mg/kg/day) and methylprednisolone (16 mg/kg/day). The survival times of enhanced animals treated with azathioprine were significantly shorter than those of animals treated with enhancing serum alone, suggesting that this agent may prevent the development of autoenhancement. Although suboptimal doses of antilymphocyte serum suppress rejection in this enhancement model, the dose requirements of conventional immunosuppressive agents appear to be maximal rather than minimal.     

Immunological enhancement of rat small intestinal allografts

In an attempt to evaluate whether survival of rat intestinal allografts could be extended by the administration of enhancing serum, Lewis-Brown Norway small intestine was transplanted to Lewis recipients, using microsurgical techniques. Only multiple injections of serum, administered on alternate days, resulted in a prolongation of survival by a few days. Neither graft irradiation nor a single injection of antiserum was effective in increasing survival time of the transplanted intestine. Clinical trials of intestinal transplantation from cadaver donors will probably have to await a clearer understanding of various methods of altering host responsiveness to foreign tissue. At the present time, central venous nutrition offers the best solution to the patient with an insufficient length of small intestine.     

Enhancement of rat renal allografts with monoclonal antibody.

Treatment of rat allograft recipients before grafting with donor spleen cells and whole, pooled antidonor alloimmune serum results in indefinite renal allograft survival. The enhancement is immunologically specific. In these experiments a monoclonal, homogenous anti-BN antibody was produced by a hybridoma clone created by fusing the mouse-P3 myeloma with spleen cells from Lewis rats immunized with BN lymphoid cells. The hybridoma supernatent enhanced survival of LBN renal allografts in Lewis recipients as effectively as whole Lewis anti-BN antiserum. Dilution of the hybridoma supernatent by tenfold or a hundredfold abrogated the enhancement effect.