H. G. Muchmore

Operation Everest II: Alterations in the immune system at high altitudes

We investigated the effects on immune function after progressive hypobaric hypoxia simulating an ascent to 25,000 ft (7620 m) over 4 weeks. Multiple simultaneousin vitro andin vivo immunologic variables were obtained from subjects at sea level, 7500 ft (2286 m), and 25,000 ft during a decompression chamber exposure. Phytohemag-glutinin-stimulated thymidine uptake and protein synthesis in mononuclear cells were reduced at extreme altitudes. Mononuclear-cell subset analysis by flow cytometry disclosed an increase in monocytes without changes in B cells or T-cell subsets. Plasma IgM and IgA but not IgG levels were increased at altitudes, whereas pokeweed mitogen-stimulatedin vitro IgG, IgA, and IgM secretion was unchanged. During exposure to 25,000 ft,in vitro phytohemagglutinin-stimulated interferon production and natural killer-cell cytotoxicity did not change statistically, but larger intersubject differences occurred. IgA and lysozyme levels (nasal wash) and serum antibodies to nuclear antigens were not influenced by altitude exposure. These results suggest that T-cell activation is blunted during exposure to severe hypoxemia, whereas B-cell function and mucosal immunity are not. Although the mechanism of alteredin vitro immune responsiveness after exposure to various environmental stressors has not been elucidated in humans, hypoxia may induce alterations in immune regulation as suggested byin vitro immune assays of effector-cell function.

Enzyme-linked immunosorbent assays in murine cryptococcosis

In this investigation, enzyme-linked immunosorbent assay (ElISA) procedures were used to study the time of appearance and the duration of demonstrable antigen and antibody in body fluids of mice with disseminated cryptococcosis. The ELISA antigen procedure detected cryptococcal capsular polysaccharide (CCP) in the serum and urine of infected mice 3 days after infection--4 days before it could be demonstrated by the latex agglutination procedure. ELISA-reactive antibody was present throughout the course of infection (mean death time, 32 days), whereas antibody was not detected by whole cell agglutination after day 20. High serum concentrations of CCP (titers to 64,000) persisted throughout the course of infection, while antibody declined to low levels with progression of disease. ELISA provides a sensitive system for quantitation and monitoring of antigen (CCP) processing and clearance (or storage), and for cryptococcal antibody formation in progressive cryptococcosis.

Delayed hypersensitivity to cryptococcin in man

Twenty-six of 82 healthy persons from a small community in Oklahoma responded to intradermal testing with cryptococcin by development of typical delayed skin reactions with induration of 5 mm. or greater in diameter. Although the hyper-reactivity to cryptococcin may be due to past exposure to C. neoformans, exact interpretation of the observed reactions cannot be definite at this time because of concomitant presence of histoplasmin sensitivity in some of the subjects tested.

Purification of labeled antibody by minicolumn gel centrifugation

Radiolabeled anti-human immunoglobulin G was purified by the elution from a minicolumn of Protein A-Sepharose by gel centrifugation. As much as 93.7% of the Protein A-bound 125I-labeled immunoglobulin G was recovered within the first three 200-μl fractions. Removal of the eluting agent was achieved by centrifuging the peak fractions through a minicolumn of hydrated Sephadex G-50.

Cell wall differences of patient and soil isolates of Cryptococcus neoformans

Two isolates of Cryptococcus neoformans were studied to determine whether or not differences in chemical composition of the cell walls existed. Aerated cultures of both isolates were grown at 37°C. in a synthetic liquid medium. A purified cell wall fraction was obtained by repeated passage of cells through a French pressure cell followed by differential centrifugation. Chemical analyses of cell wall fractions of each of these strains showed quantitative differences in 3 major groups of compounds. The isolate from the patient contained a higher percentage of hexose and a lower percentage of hexosamines and lipids than did the soil isolate.