Michael C. Jones

Postirradiation recovery of lymphoid cells in the rat

Evidence for a unique class I MHC antigen (termed Pa), which is believed to be expressed on rat trophoblast during pregnancy and which stimulates alloantibody formation with unusual interstrain cross-reactivity, has been examined in inbred rats. The previously reported pattern of crossreactivity was confirmed but was not unique to antisera produced by pregnancy. Antibody blocking studies using biotinylated rat monoclonal antibodies to distinct epitopes on RT1Aa antigens suggested that antibodies present in pregnancy sera, especially from multiparous rats, reacted with several epitopes on these molecules. Moreover, a rat monoclonal antibody, 381- 1E10, directed against the putative Pa epitope was shown by synergistic lysis and cold antibody competition to be directed to the immunodominant S epitope on RT1Aa. These data argue against the existence of a distinct Pa antigen or epitope detected by pregnancy sera.

An immunohistological study of epidermal growth factor receptor and neu receptor expression in proliferative glomerulonephritis

&NA; Many forms of glomerulonephritis including IgA nephropathy are characterized by mesangial cellular proliferation. Since epidermal growth factor is a potent mitogen for cultured human mesangial cells, we have attempted to localize and quantify the expression of its receptor in normal and abnormal renal biopsies using immunohistochemistry. Using a particular antibody (Amersham, clone EGFR1), the epidermal growth factor receptor (EGF‐R) was shown to be predominantly localized in the mesangium of the glomerulus. Visual estimates of intensity of staining suggested that expression of this receptor may be increased in some IgA disease patients with mesangial proliferative glomerular lesions. The neu receptor which has a 50% homology with EGF‐R was, however, absent from the glomerulus and cultured mesangial cells did not express detectable levels. Expression of EGF‐R by cultured mesangial cells, as assessed by immunostaining, was weak and it was not possible to induce detectable upregulation using different cytokines. The factors leading to increased expression of EGF‐R in glomerulonephritis, therefore, remain unknown. Our findings suggest that signalling via EGF‐R may play a role in the pathogenesis of proliferative glomerulonephritis. Despite its homology with EGF‐R, the neu receptor is unlikely to have similar importance.

Reduction Of Sensitization Induced By Blood Transfusion In The Rat By Monoclonal Antibodies

Primary and secondary alloantibody responses were monitored in (AOxPVG)F1 hybrid rats after three transfusions of DA blood; the initial transfusion was either untreated or pretreated with monoclonal antibody directed to class I antigens or other cell surface markers. Mean antibody activity in recipient sera against class I DA antigens was significantly decreased by pretreatment with the monoclonal antibodies. The most marked suppression was associated with pretreatment by antibodies to the four major nonoverlapping epitopes of the RT1Aa antigen. Subsequent transfusions of DA blood failed to stimulate a secondary response. Crossreactivity of the alloantibody reactivity with BDIX antigens was diminished by pretreating the transfusions with rat anti-RT1A antibodies and, to a lesser extent, with a mouse monoclonal antibody (OX-18) to a common class I determinant. Monoclonal antibody pretreatment had no effect on the humoral response to class II DA antigens. These studies indicate that blood transfusions pretreated with monoclonal antibodies induce a less-potent cytotoxic humoral immune response and that reactivity is most effectively suppressed by completely masking the class I antigen. This technique may prove of clinical value in preventing the sensitization caused by blood transfusions in potential transplant recipients.

THE INFLUENCE OF REPEATED TRANSFUSIONS AND CYCLOSPORINE ON SECONDARY ALLOANTIBODY RESPONSES IN INBRED RATS

The influence of cyclosporine (CsA) on secondary and established alloantibody responses was evaluated in inbred Lewis rats and (AOPVG)F1 hybrid rats. Lewis rats received weekly transfusions of DA whole blood for 8 weeks either with or without cyclosporine (15 mg/kg/ day) after sensitization with DA splenocytes. Hybrid rats received only CsA (10 mg/kg/day) after similar sensitization. Administration of CsA did not affect the spontaneous decline in alloantibody titers against class I (RT1A) antigens, but it was associated with a significantly reduced response to class II (RT1B) antigens at the end of the study. CsA prevented maintenance of high alloantibody titers to RT1A antigens in Lewis rats transfused repeatedly following sensitization. IgG alloantibody subclass responses were also altered by CsA with significant reduction in titers of IgG1, 2a, and 2b against RT1A antigens in rats transfused repeatedly; CsA did not, however, suppress IgG2c alloantibody levels in these animals. Responses to public RT1A antigens disappeared in most animals irrespective of their treatment group, whereas those to private and public RT1B antigens persisted unless CsA was administered. The results suggest that, contrary to results obtained with other antigens, CsA does influence secondary alloantibody responses. CsA may thus prove of value in highly sensitized dialysis patients who require further blood transfusions.

Alloantibody and Transferable Suppressor Activity Induced By Cyclosporine and Blood Transfusions in the Rat

The effect of cyclosporine on the alloantibody response to blood transfusion was investigated in inbred strains of rats by IHA and CELISA; recipient animals differed from the donors at the class I (RT1A) or both class I and class II (RT1B) antigens of the major histocompatibility complex. Alloantibody titers stimulated in high responder PVGu/c animals by blood transfusions were attenuated by cyclosporine; this effect was not demonstrated in low responder PVGc rats, as alloantibody titers decreased after further blood transfusions whether or not cyclosporine was given. Cyclosporine not only reduced the initial IgM response but suppressed the subsequent production of IgG. Splenocytes from rats receiving cyclosporine and blood transfusions from donors that differed from the recipients at the class I antigen were effective in suppressing the subsequent antibody response to blood transfusion. When blood transfusions from donors which differed from the recipients at both class I and class II antigenic loci were given after splenocyte transfer, a greater degree of immunosuppression was detected than if the transfusion donor differed only at the class I locus. These data suggest that the sensitization produced by blood transfusions and the persistence or decline of the alloantibody response depend upon the responder status of the recipient. Blood transfusions given with cyclosporine are capable of inducing suppressor activity that is transferable in spleen homogenates. Subsequent alloantibody responses are influenced by the class I and class II disparities of the donor and recipient animals. If these results can be extrapolated to clinical practice, cyclosporine should be given with pretransplant blood transfusions to prevent sensitization, and the transfusion donor should differ from the recipient at both class I and class II antigenic loci.

Prevention of graft rejection by cyclosporin A in man

Preventing graft rejection remains the single most important challenge facing the clinician in organ transplantation. Since the immunological basis of rejection was first recognized, attempts have been made to modify the host response to foreign antigens in order to prevent rejection and possibly engender graft tolerance — a state in which the graft is no longer recognized as foreign by the host This ideal is not yet possible in clinical practice but a variety of techniques have evolved to suppress the patient’s immune response and prevent or suppress rejection. In the 1950s immunosuppression in the form of total-body irradiation was used, but because of associated morbidity and mortality was superseded in the 1960s by drug therapy — most commonly using combined treatment with azathioprine and prednisolone. This combination enabled renal transplantation to become a successful mode of therapy for patients with end-stage renal disease such that by the late 1970s it could be said to be the most effective and economical form of treatment1, allowing the patient to return to near-normal health and activities.