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The present study investigated the expression of the complement receptor type 1 (CR1) on the membrane of erythrocytes (CR1/E) of patients with systemic lupus erythematosus (SLE) by flow cytometry. We found a significant reduction in CR1/E numbers in SLE patients (n = 52), compared to controls (512 +/- 171 and 689 +/- 146, respectively, P = 0.0001). Reduction was more pronounced in active disease patients. The mean CR1/E number observed in patients with inactive disease was 546 +/- 163 CR1/E, while active SLE patients presented a mean of 385 +/- 133 CR1/E (P = 0.001). Patients with SLE with similar activity indexes tend to have similar CR1/E numbers, irrespective of disease severity. We also observed a trend to CR1/E reduction in severe nephritis patients. A small group of SLE patients with chronic renal failure and inactive disease showed CR1/E numbers nearly identical to controls (689 +/- 146 versus 686 +/- 123, respectively, P = 0.95). This was the only group of SLE patients with normal CR1/E numbers. These results confirm the CR1/E reduction in SLE patients as previously described, and also suggest that this reduction is related to disease activity and not to disease severity.

In order to investigate further the adaptive response of moulds to ambient pH, we have measured by ELISA the pho-2-encoded Pi-repressible alkaline phosphatase synthesised by Neurospora crassa. We showed that the 74A and pho-2A strains of this mould secrete similar amounts of the pho-2-encoded enzyme irrespective of ambient pH, when both the preg and pgov genes are not functional, i.e., in strains nuc-2 + growing under Pistarvation. This suggests that pho-2, which is responsive to Pi starvation via the action of genes nuc-2, preg, pgov and nuc-1, is not a gene responsive to ambient pH and that the differential glycosylation observed for the Pi-repressible alkaline phosphatase retained by the mycelium at pH 5.6 or secreted into the growth medium at pH 8.0 is the genetic response to ambient pH sensing in N. crassa.

Summary. In order to understand the mechanism of complement (C) activation by immune complexes (ICs), the anti-complementary effect of ICs containing cationized antigens was compared in vitro to that using ICs formed by native antigens. ICs were prepared with affinity-purified rabbit polyclonal IgG antibovine serum albumin (BSA) antibody and either native BSA (isoelectric point 4.2) or BSA rendered cationic by treatment with ethylenediamine (isoelectric point 9.4). Native and cationized antigens were characterized by isoelectric focusing. ICs containing anti-BSA IgG or F(ab H ) 2 , formed either at equivalence or in excess of native or cationized antigen, were submitted to ultracentrifugation in a sucrose gradient for mesh size determination. The anti-complementary effect of ICs was evaluated by kinetic determination of haemolytic activity of human serum on haemolysinsensitized sheep red blood cells. In conditions of antigen excess, the ICs formed by cationized BSA were significantly more efficient in activating human complement than those formed by native antigen. This higher activity was dependent on cationized antigen complexed with complete antibody molecules, as non-complexed cationized BSA or ICs prepared with F(ab H ) 2 fragments were inactive under the same experimental conditions. Furthermore, this difference did not depend on the mesh size of the immune Correspondence: Luciana Simon Pereira Crott, Departamento de Ana  lises Clõ Ânicas, Toxicolo  gicas e Bromatolo  gicas,

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