Prasanta K. Ray

Rescue of rats from large dose cyclophosphamide toxicity using protein A

SummaryCyclophosphamide (Cy) is widely used as an effective cytotoxic drug, but its use is limited because of its toxicity. In this report, we describe for the first time the ability of purified protein A (P) of Staphylococcus aureus to reduce Cy-induced toxicity in rats. Protein A-treated animals recover quickly from the toxic effects of Cy. The antitumor property of Cy is not reduced in the P+Cy group. In fact, the latter showed a persistent decrease in tumor volume compared with the Cy group. Protein A may prove to be an effective agent in increasing the therapeutic index of Cy.

Failure of neuraminidase to unmask allogeneic antigens on cell surfaces.

Summary Vibrio cholerae neuraminidase (VCN) does not lyse mouse lymphoid cells at any concentration up to 250 units/ml/5 × 106 cells. VCN treatment of C3H/HeJ lymphoid cells increases their susceptibility to lysis with C57 anti-C3H serum and complement. It does not, however, increase the capacity of these cells to absorb C57 anti-C3H complement-fixing antibody. Thus, neither the increased susceptibility to lysis nor the increased allogeneic immunogenicity of VCN-treated lymphoid cells is due to an unmasking of more allogeneic antigens on the cell surface.

Unmasking of Xenogeneic Neo-antigens on Mouse Lymphoid Cell Surfaces by Vibrio cholerae Neuraminidase

Summary C3H/HeJ mouse lymphoid cells treated with Vibrio cholerae neuraminidase (VCN) are more easily lysed by normal rabbit, normal guinea pig, and normal human sera than are untreated cells or cells exposed to heat-inactivated VCN. Absorption studies suggest that VCN does not unmask a greater number of previously available xenogeneic specificities on the cell surface. Instead, VCN appears to unmask new antigens for which preformed antibodies also exist in xenogeneic sera.

Effect of Concanavalin A and Phytohemagglutinin on the Modification of Immunogenicity of Canine Kidney Allografts

Mongrel dog kidneys were allografted to unrelated nephrectomized recipients which were then treated with subimmunosuppressive doses of azathioprine (2.5 mg/kg/day). Dog kidneys treated in vitro with perfusates containing concanavalin A (Con A) or phytohemagglutinin-P (PHA) survived as long as 60 days (mean 39.8 +/- 4.3) after transplantation, whereas normal kidneys survived less than 16 days. The optimal prolongation was achieved by perfusing the kidneys with 500 ml Ringers lactate containing 25 mg/L Con A, 25 4 degrees C. Lesser effects were achieved with higher or lower concentrations of Con A, or with perfusions carried out at 25 degrees C. Most evidence suggests that Con A and PHA bind to cell surfaces and interfere with the perception of the graft antigens by the host.