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The mechanisms of stress-related immune alterations have not been fully elucidated. Cell-mediated immune responses as well as antibody and certain cytokines are reported as being suppressed during times of high stress. However, the role of suppression vs dysregulation has not been established in human stress models. The effect of exam stress on regulatory cytokines in 16 healthy medical students was assessed by measuring type-1 (IFN-γ) and type-2 (IL-10) cytokines from 72-h PHA/PMA-stimulated PBMC 4 weeks before and 48 h after exams. Results demonstrated decreased IFN-γ accompanied by increased IL-10 during exam stress that resulted in a decreased IFN-γ:IL-10 ratio. There was a significant correlation between the cytokine response to PHA/PMA and number and subjective adjustment to daily hassles. Additionally, students who reported greater levels of loneliness also reported greater numbers of and poorer subjective adjustment to hassles. The differences were consistent in both males and females but did not correlate with AM cortisol levels. Additionally, when individuals were grouped into high vs low preexam hassle levels, the type-1/type-2 shift in the IFN-γ:IL-10 ratio occurred in the low hassles group only. These data suggest that psychologically stressful situations shift type-1/type-2 cytokine balance toward type-2 and result in an immune dysregulation rather than overall immunosuppression. This may partially explain the increased incidence of type-2-mediated conditions such as increased viral infections, latent viral expression, allergic/asthmatic reactions, and autoimmunity reported during periods of high stress.

Chitosan, a cationic polysaccharide, has been widely used as a dietary supplement and in a variety of pharmacological and biomedical applications. The antifungal activity and mechanism of action of low molecular weight water-soluble chitosan (LMWS-chitosan) were studied in fungal cells and vesicles containing various compositions of fungal lipids. LMWS-chitosan showed strong antifungal activity against various pathogenic yeasts and hyphae-forming fungi but no hemolytic activity or cytotoxicity against mammalian cells. The degree of calcein leakage was assessed on the basis of lipid composition (PC/CH; 10:1, w/w). Our result showing that LMWS-chitosan interacts with liposomes demonstrated that chitosan induces leakage from zwitterionic lipid vesicles. Confocal microscopy revealed that LMWSchitosan was located in the plasma membrane. Finally, scanning electron microscopy revealed that LMWS-chitosan causes significant morphological changes on fungal surfaces. Its potent antibiotic activity suggests that LMWS-chitosan is an excellent candidate as a lead compound for the development of novel anti-infective agents

The trypanosomes and Leishmania species are parasitic protozoa that afflict millions of people throughout the world. If not treated, African trypanosomiasis and visceral leishmaniasis are fatal. The available drugs are severely limited by toxicity, marginal efficacy, the requirement for parenteral administration, and spreading drug resistance. In this study, a spectrophotometric assay was developed and validated for measuring the cytotoxicity of test compounds against axenically cultured bloodstream-form Trypanosoma brucei (African trypanosomes) and promastigotes of Leishmania donovani. Enzymatic hydrolysis of p-nitrophenyl phosphate, monitored by a microtiter plate reader, is a reliable surrogate for parasite cell counts. The assay is simple, inexpensive, and highly reproducible. The coefficient of variation for EC₅₀ values is <10% for determinations obtained over several months. This method permits the rapid screening of candidates for much-needed new drugs against these parasites.