We find a favorable prognosis for the majority of children who are treated for meningitis caused by H. influenzae type b.

The kinetics of phagocytosis of Candida albicans by human polymorphonuclear leukocytes was studied. The basis for these studies was a phagocytic assay with use of C. albicans radiolabeled with [3H]adenine. After incubation of leukocytes with C. albicans, extracellular C. albicans was separated from phagocytes by centrifugation through Ficoll-Hypaque suspensions (specific density, 1.175 g/cm3). Recovery of leukocytes by this technique was greater than or equal to 85%. The initial rate of phagocytosis was more rapid than that previously reported for bacteria. Ethylenediaminetetraacetate, vinblastine, ethylmaleimide, NaF, and ice bath temperature completely inhibited phagocytosis. Colchicine had no effect, and NaN3 was partially inhibitory. Pooled sera possessed low titers (greater than or equal to 1:40) of heat-stable opsonins. The opsonic activity of pooled sera was shown to depend primarily upon complement activated through both the alternative and classical pathways. Decomplemented hyperimmune sera were opsonic at high dilutions (greater than or equal to 1:160), and complement amplified the initial rate of ingestion seen with hyperimmune sera.

Depressed chemotactic activity of polymorphonuclear leukocytes (PMNL) infected with influenza virus could be due to changes occurring at the plasma membrane. The present study examined the effect of unopsonized influenza virus on chemotaxis, adherence, receptor binding, shape change, membrane fluidity, and release of specific granules from PMNL. Chemotactic activity of PMNL under-agarose to the chemoattractants, zymosan-activated serum ( ZAS ) and N-formyl-methionyl-leucyl- phenylalanine (fMLP), and adherence of PMNL to a plastic surface were markedly decreased in virus-treated cells as compared to control cells. The binding of fMLP to the PMNL was increased in virus-treated cells compared with control cells. Exposure of cells to virus, ZAS , or fMLP caused 35%-50% of the cells to become bipolar in shape, whereas less than 5% of the cells exposed to buffer became bipolar. Influenza virus did not alter membrane fluidity as measured by electron spin resonance spectroscopy with the probe 5-doxyl stearate. Virus-treated PMNL stimulated with FMLP or Staphylococcus aureus exhibited a marked decrease in the amount of lactoferrin released into phagosomes, onto the cells' outer membrane, and into the extracellular medium as compared to control cells. The possible relationship between inhibition of lysosomal enzyme degranulation and decreased chemotactic activity and adherence of PMNL is discussed.

Changes in the light transmission of suspensions of activated neutrophils are widely used to measure the dynamics of neutrophil aggregation. Such studies have suggested, for example, that aggregation is irreversible for human newborn neutrophils but fully reversible for adult cells. We have evaluated aggregation directly by microscopic particle counting and compared it with changes in light transmission (delta T) and with release from three granule subsets for neutrophils activated with N-formyl-methionyl-leucyl-phenylalanine (FMLP). Maximal increases in %T in response to 0.5 micromol/L FMLP were approximately 25% larger for newborn than for adult neutrophils, and were only partially reversible by 8 minutes, while %T increases for adult neutrophils were fully reversible. However, measurements of neutrophil aggregation using light microscopy showed that both newborn and adult neutrophils fully deaggregated. A further independence of delta T from aggregation was found by pretreating adult neutrophils with cytochalasin B (5 micrograms/mL) in the presence of 0.5% gelatin, a pretreatment that blocked FMLP-induced neutrophil aggregation while allowing large increases in %T and degranulation. In response to FMLP, newborn neutrophils released more enzyme from each granule subset than did adult neutrophils. Our results suggest that cellular events associated with neutrophil activation (other than aggregation) are implicated in light transmission responses and that these differ for adults and newborns. These results also suggest that reports of neutrophil aggregation should be based on direct particle counting methods rather than on %T responses.

The mechanism by which influenza virus interferes with polymorphonuclear leukocyte (PMN) chemotaxis was investigated. Incubation of human PMN with influenza A virus in vitro for 30 minutes significantly decreased PMN migration under agarose in response to N- formyl-methionyl-leucyl-phenylalanine (FMLP) or zymosan-activated serum. Virus-treated PMN tended to aggregate in the under-agarose assay. Aggregation was avoided by using a more dilute PMN suspension in filter assays. Virus treatment significantly decreased migration through 100-micron thick cellulose nitrate filters but had no effect on migration through 10-micron thick polycarbonate filters or on PMN bipolar shape change. Virus was not chemotactic in the polycarbonate filter assay and did not induce shape change in purified PMN. It was concluded that influenza virus did not interfere with the ability of PMN to recognize a chemoattractant, undergo shape change, and move a short distance but did limit the extent of migration. Inhibition could not be explained by chemotactic deactivation, since the virus was not chemotactic.