Soluble immune complexes in lupus mice: clearance from blood and estimation of formation rates.

Elevated levels of circulating immune complexes (IC) occur in patients with systemic lupus erythematosus (SLE) and in several strains of mice that spontaneously develop a lupus-like illness. An increase in circulating IC might occur as a result of increased IC formation or decreased IC clearance. Previous work with one murine lupus strain, NZB/W, demonstrated normal clearance of soluble IC.

Failure of methotrexate and methylprednisolone to alter the clearance of model immune complexes.

We evaluated the effect of methotrexate (MTX) and methylprednisolone (MP) on reticuloendothelial system (RES) clearance of soluble model immune complexes (IC) in BALB/C mice. MTX was administered by intraperitoneal route either as a single dose (0.5 mg/kg) or as 10 alternate day doses (0.

Monocyte receptors for the Fc portion of IgG are increased in systemic lupus erythematosus.

Defective clearance of IgG-sensitized particles has been documented in systemic lupus erythematosus (SLE). This defect may be of pathogenetic significance because it allows the prolonged circulation of endogenous immune complexes with subsequent tissue deposition. To assess the possible contribution of a genetically determined defect in phagocyte Fc-IgG receptor expression or immune complex saturation of Fc-IgG receptors to impaired clearance, we used a well-characterized monomer binding assay to quantitate monocyte Fc-IgG receptors in normal controls and in 26 patients with SLE.

Convexity theorem for subthreshold stimuli in linear models of visual contrast detection.

Under the general assumption that visual contrast detection occurs by a parallel array of linear detectors, either without probability summation or with probability summation of a commonly assumed type, it is shown that the set of functions representing subthreshold stimuli must be convex. Thus, for example, a planar plot of the threshold locus using multiples of any two functions as axes, must be convex (cannot bulge inward). If experimental evidence to the contrary were discovered, it would rule out detection by parallel linear detectors of the above type.

Spatial summation effects on two-component grating thresholds.

Some experimental studies of subthreshold summation between sinusoidal grating components have been interpreted as showing very narrow channel bandwidths in human visions. This paper discusses an alternative interpretation of these experiments based on consideration of probability-summation effects among spatially distributed detectors. We conclude that frequency-selective channels must still be hypothesized in order to fit the data, but the channel bandwidth may be much wider than earlier interpretations suggest.