Distinct properties of Thy-1 antibodies elicited in rats by immunization with mouse brain.

Rats are known to possess antigenic determinants related to the Thy-1.1 allele. Immunization of rats with brain homogenates from mice carrying either the Thy-1.1 or the Thy-1.2 alleles resulted in the production antisera which were cytotoxic for thymus cells of both strains of mice. Lymph node, spleen and cortisone-resistant thymus cells were refractory to the cytotoxic effect of rat anti-mouse brain sera. Peripheral lymphocytes were fully capable of absorbing the cytotoxic activity of the sera on thymus cells, although the concentration of the antigen on their cell surface was considerably less than on thymus cells. Blocking experiments with allo- and xenoantisera to Thy-1 antigens suggested that the antigen detected by rat anti-mouse brain sera is related to the Thy-1 system. The Thy-1 specificity detected by rat antisera seems to differ from previously described Thy-1 antigens in that it attains a high concentration on thymus cells but is relatively deficient in its expression on peripheral T cells.     

The association of H-2 antigens and EAC receptors on the surface of peritoneal cells.

The exposure of murine peritoneal cells to anti-H-2 sera results in a diminished expression of H-2 antigen on the cell surface. Concomitant with this "H-2 modulation" the capacity of macrophages to bind sheep red blood cells coated with antibody and complement (EAC) was markedly diminished. In contrast, there was no change in the capacity of modulated macrophages to bind sheep red blood cells coated with antibody alone (EA). Antibodies to K end H-2 specificities were more effective in reducing the binding of EAC than antibodies to D end H-2 specificities. Exposure of peritoneal cells to O or Ly antisera had no effect on the formation of EAC rosettes. Exposure of peritoneal cells to anti-H-2 sera, under conditions which would not allow modulation of H-2 antigens, also prevented the reduction of EAC binding. Thus, the EAC receptors and H-2 antigenic specificities seem to be closely related on the surface of peritoneal cells, but constitute distinct cell surface structures. Preliminary evidence indicates that vinblastine, a microtubule depolymerizing agent, may disrupt the close association of EAC receptors and H-2 antigens. It is suggested that the association of EAC receptors and K end H-2 determinants on the membrane of macrophages may have implications for the regulation of the immune response by H-2-linked Ir genes.     

Formation of RNA and protein in cells infected with standard and defective Sindbis virus

Our studies on the formation of Sindbis virus proteins have established that: 1. one of the two envelope proteins (E2) accumulates in infected cells as a higher molecular weight precursor that is slowly converted to the virion protein; 2. the large protein (mol. wt 130000 daltons), that accumulates in cells infected with a temperature-sensitive mutant of Sindbis virus contains sequences of the three virion proteins; and 3. the protein (mol. wt. 100000 daltons) isolated from BHK cells infected with Sindbis virus is related in sequence to the two envelope proteins.We have investigated the formation of defective-interfering (DI) particles of Sindbis virus and their ability to inhibit the replication of standard virus. BHK cells infected with passages of Sindbis virus containing DI particles accumulate a species of RNA (20S) that is about half the molecular weight of the 26S RNA. We have demonstrated by competitive hybridization experiments that 20S RNA contains half the sequences of 26S RNA. We also present evidence that in contrast to 26S RNA, 20S does not bind to polysomesin vivo and is not translatedin vitro.Presented on the Meeting on Studies on Virus Replication of the Commission of the European Communities in Brüssel, May 1974.     

Concentrations of Soluble CD95 and CD8 Antigens in the Plasma and Levels of CD8+CD95+, CD8+CD38+, and CD4+CD95+ T Cells Are Markers for HIV-1 Infection and Clinical Status

Apoptosis mediated via the CD95 (FAS/APO-1) receptor is thought to play a role in the depletion of CD4+ T cells in HIV infection. In the present study expression of the CD95 antigen on lymphocyte subsets and the plasma level of soluble CD95 (sCD95) were determined in HIV-1-infected adults. The expression of CD95 was increased on CD8 cells in all groups of HIV+ individuals, while increased expression of CD95+ cells on CD4 cells was limited to individuals with CD4 counts of <200 mm³. The proportion of CD4+ that expressed CD95 was inversely correlated with the percentage of CD4+ PBL. The concentration of sCD95 was significantly higher in the plasma of HIV-infected individuals than in normal controls. The level of sCD95 in HIV-infected subjects showed no correlation with the percentage of PBL expressing CD95, indicating that the increased level of sCD95 did not reflect release from CD95+ PBL. The plasma sCD95 concentration was significantly correlated with the percentage of CD8+ cells and, particularly, with CD8+CD38– cells. A striking inverse correlation was found between the sCD95 plasma concentration and the proportion of CD4+CD95+ cells out of the total CD4+ population. There was no correlation between the serum level of sCD95 and that of soluble CD8 (sCD8), both of which were increased in the plasma of HIV+ individuals. Unlike the level of sCD95, the level of sCD8 in the plasma of HIV+ individuals. Unlike the level of sCD95, the level of sCD8 in the plasma of HIV+ individuals was correlated with the percentage of CD95+ and CD8+CD38+ cells. The present study indicates that plasma sCD95 may be one of the factors that regulate apoptotic death of lymphocytes in HIV infection.     

No exit? The effect of health status on dissatisfaction and disenrollment from health plans.

OBJECTIVE: To examine the implications of serious and chronic health problems on the willingness of enrollees to switch health plans if they are dissatisfied with their current arrangements. DATA SOURCE: A large (20,283 respondents) survey of employees of three national corporations committed to the model of managed competition, with substantial enrollment in four types of health plans: fee-for-service, prepaid group practice, independent practice associations, and point-of-service plans. STUDY DESIGN: A set of logistic regression models are estimated to determine the probability of disenrollment, if dissatisfied, controlling for the influence on satisfaction and disenrollment of age, race, education, family income and size, gender, marital status, mental health status, pregnancy, duration of employment and enrollment in the plan, number of alternative plans, and HMO penetration in the local market. Separate coefficients are estimated for enrollees with and without significant physical health problems. Additional models are estimated to test for the influence of selection effects as well as alternative measures of dissatisfaction and health problems. DATA COLLECTION: Data were collected through a mailed survey with a response rate of 63.5 percent; comparisons to a subsample administered by telephone showed few differences. PRINCIPAL FINDINGS: In group/staff model HMOs and point-of-service plans, only 12-17 percent of the chronically ill enrollees who were so dissatisfied when surveyed that they intended to disenroll actually left their plan in the next open enrollment period. This compared to 25-29 percent of the healthy enrollees in these same plans, who reported this level of dissatisfaction and 58-63 percent of the enrollees under fee-for-service insurance. CONCLUSIONS: Switching plans appears to be significantly limited for enrollees with serious health problems, the very enrollees who will be best informed about the ability of their health plan to provide adequate medical care. These effects are most pronounced in plans that have exclusive contracts with providers. We conclude that disenrollment provides only weak safeguards on quality for the sickest enrollees and that reported levels of dissatisfaction and disenrollment represent inaccurate signals of plan performance.     

Development of a brief questionnaire for screening for multiple chemical sensitivity syndrome

The objective of this study was to identify a parsimonious set of questions that has high sensitivity and specificity for screening for individuals with multiple chemical sensitivity (MCS) syndrome. We performed a cross-sectional survey using a case-control design. Subjects were derived from patients seen at an academically based Occupational and Environmental Medicine Clinic. Cases consisted of patients who fulfilled the Cullen definition for MCS. Controls were patients who had diagnoses excluding MCS and asthma and who were matched to cases by age and sex. Cases and controls filled out a screening questionnaire that, among things, elicited responses as to whether and how subjects reacted to 122 different types of environmental exposures. Data from 44 pairs of cases and controls were available for analysis. The average age of cases was 50.2 years, and 91% was female. Among cases, the most common exposure that was purported to incite MCS was 'indoor air quality contaminants (unspecified)' (59%), followed by solvents (27.3%). After randomly excluding five cases and controls, a stepwise selection procedure for two-group discriminant analysis revealed that the main contributors to the discrimination of the remaining cases and controls were self-reported reactions to copy machine emissions, marking pens, aftershave, window cleaner, nylon fabric, pine-scented products, and rayon material. When a positive response to these factors was used as the sole method for discriminating cases from controls, only one of 41 cases was misclassified as a control while none of the controls was misclassified as a case. When the same method was applied to the five excluded cases and five excluded controls, only one of the five cases was misclassified while none of the five controls was misclassified as a case. Among patients with MCS defined by the Cullen criteria in this clinical setting, having a reaction to these seven common potential exposures comprised a parsimonious set of factors that discriminated between MCS patients and age- and sex-matched normal controls. These questions may have utility in screening for individuals with MCS in general population survey studies.     

Surveillance of antimicrobial prophylaxis for surgical procedures.

OBJECTIVE: To assess the practice of antimicrobial prophylaxis for surgical procedures in eight surgical departments in a 550-bed teaching hospital. METHODS: A list of all major procedures performed in our hospital, with recommendations for prophylaxis based upon the literature, has been distributed since 1993 and is updated periodically. The practice of surgical prophylaxis between January 1 and March 31, 1996, was examined by assessing four variables: (1) Did the particular procedure justify prophylaxis, and was it provided? (2) Was timing optimal, ie, within 1 hour prior to surgery? (3) Was the appropriate antimicrobial selected? (4) Was duration optimal, ie, < or =24 hours? RESULTS: During the study period, 2,117 operations were performed, of which 1,631 (77%) were reviewed. Sixty-six percent were clean surgery, 28% clean-contaminated, and 6% contaminated; 72% of procedures were elective, 28% emergencies. Of 1,631 operations requiring prophylaxis, 1,142 (70%) received it, 489 (30%) did not. Of 1,631 patients, 1,392 (85%) received appropriate care: 929 (67%) appropriately received prophylaxis, and 463 (33%) appropriately did not receive prophylaxis. Of 955 patients who received prophylaxis, 26 (3%) did so inappropriately. Of 1,142 patients who should have received prophylaxis, 213 (19%) did not receive it. Female gender, clean surgery, elective operations, and infrequently performed procedures were all significant indicators of inappropriately withheld prophylaxis (P<.001). In addition, the rate of appropriately provided prophylaxis varied between departments from 71% to 97% (P<.001). Assessment of the 929 procedures for which prophylaxis was justified and given revealed that 100% of patients received it on time, the choice of antimicrobial was appropriate in 95% of cases, and duration was < or =24 hours in 91%. CONCLUSIONS: Audits of surgical prophylaxis are expected to detect different errors in different institutions. Conducting audits of surgical prophylaxis probably should be part of the routine activity of infection control teams. Feeding the information back to surgeons could improve adherence to recommended guidelines and might contribute to reduced wound infection rates.     

Defective acidification of endosomes in Chinese hamster ovary cell mutants "cross-resistant" to toxins and viruses.

Like many physiological ligands, several viruses and toxins enter mammalian cells through receptor-mediated endocytosis. Once internalized, the nucleic acids of several viruses and the toxic subunit of diphtheria toxin gain access to the cytosol of the host cell through an acidic intracellular compartment. In this report, we present evidence that one class of mutants of Chinese hamster ovary (CHO)-K1 cells, which is "cross-resistant" to Pseudomonas exotoxin A, diphtheria toxin, and several animal viruses, has a defect in acidification of the endosome. Cells were allowed to internalize fluorescein isothiocyanate-conjugated dextran before subcellular fractionation. Fluorescence measurements on subcellular fractions permitted measurement of the internal pH of the isolated endosomes and lysosomes. Our results show that (i) endosomes and lysosomes from CHO-K1 cells maintain an acidic pH, (ii) acidification of both endosomes and lysosomes is mediated by a Mg2+/ATP-dependent process, (iii) GTP can satisfy the ATP requirement for acidification of lysosomes but not of endosomes, and (iv) at least one class of mutants that is cross-resistant to toxins and animal viruses has a defect in the ATP-dependent acidification of their endosomes. These studies provide biochemical and genetic evidence that the mechanisms of acidification of endosomes and lysosomes are distinct and that a defect in acidification of endosomes is one biochemical basis for cross-resistance to toxins and viruses.