c or reduced phenazine methosulfate coupled with the reduction of ubiquinone. We wish to report now that chromatophores from aerobically grown R. spheroides, strain Ga, sensitize these reactions efficiently (with quantum requirements of a few quanta per electron transfer), whereas chromatophores from the nonphotosynthetic mutant strain PM-8 are entirely unable to drive these photochemical processes. The failure of strain PM-8 to catalyze the photooxidation of reduced phenazine methosulfate is the more remarkable because this reaction is sensitized by purified bacteriochlorophyll in vitro. These findings show that the major component of bacteriochlorophyll is inert with respect to the foregoing light-induced activities, and that a special kind of reaction center is needed for the photochemistry that leads to photosynthesis. The results of experiments with exogenous reagents will be published in detail elsewhere. We are indebted to Dr. W. S. Zaugg for making available both the chemicals and the methodology for studying the photochemical electron transfer reactions of cytochrome, phenazine methosulfate, and ubiquinone. * Contribution no. 157 from the Charles F. Kettering Research Laboratory.

1. Blood group substances have been prepared from human saliva, stomach, and amniotic fluid from individuals of blood group A1 and A2. Several of the saliva samples were obtained from individuals shown to be heterozygous, A1O. 2. The purified blood group A substances from human sources were similar in nitrogen, glucosamine, reducing sugar, and acetyl content. The A1 and A2 substances differed in optical rotation. All of the human A samples were levorotatory while those from hog stomach were dextrorotatory. 3. By two immunochemical criteria the various human preparations could be shown to fall into distinct groups, with respect to purity. The best products showed maximal activity and almost all of their glucosamine was specifically precipitable by anti-A. These samples of human A substance were only about one-half as effective in precipitating antibody to hog A substance formed in man as was homologous hog A substance although the same total amount of antibody was precipitable by excess of either antigen. 4. Human blood group A1 substance was found to be antigenic in individuals of blood groups B and O but was not as good an antigen as hog A substance.

A B S T R A C T Renal tissues from two groups of patients were studied with fluorescein-labeled (Fl-) antibodies (Abs) to immunoglobulins, complement, and antibodies prepared in rabbits against BSA conjugate of 5-methyluridine (T) and cytidine (C), the latter two of which react specifically with denatured DNA. The first group consisted of 13 SLE patients, and the second consisted of 53 patients with non-SLE nephropathies. The data obtained from the two groups of patients were used for comparison, and they showed the following:(a) Fl-Abs to immunoglobulins and complement were bound in the glomeruli of tissues from all patients with active SLE glomerulonephritis characterized by deposits of foreign material in glomerular capillary walls (GCW). The fluorescent pattern was granular, corresponding to the distribution of the glomerular deposits, as seen by electron microscopy. Fl-Abs reactive with thymine and cytosine were bound in the GCW of eight of the nine patients with active SLE glomerulonephritis and showed the same granular distribution. The capacity of these latter Fl-Abs to stain the GCW was removed by absorption with the homologous antigen or denatured DNA.(b) Fl-Abs to immunoglobulins, complement, and pyrimidine bases of DNA did not react with the GCW of two SLE patients without clinical and histologic evidence of glomerulonephritis or with the sclerotic glomeruli of two uremic patients with chronic "burned out" lupus nephritis.(c) The glomeruli of 47 of the 53 patients with other nephropathies bound Fl-Abs to immunoglobulins and

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