This program project proposes to investigate the nephritogenic and transplantation activities of the streptococcal membrane and soluble fractions derived from it. Soluble fractions have been obtained from the streptococcal membrane which are on chemical analysis found to be low molecular weight glycoproteins which demonstrate several immunological and biological properties. These materials are immunologically cross- reactive with similar materials obtained from human glomerular basement membrane, induce homograft sensitivity in outbred mice to skin homografts and abrogate the cytotoxic activity of anti-HL-A antisera. These materials are being evaluated in in vitro correlates of cellular immunity in patients with rheumatic fever and post-streptococcal glomerulonephritis. Additionally, they are mitogenic for most human lymphocytes evaluated and may be involved in abrogating or altering MLC in humans. It is our intent to chemically characterize the effector molecules of the soluble fractions and to alter them so that they may be further explored in the above experimental parameters.