Lack of evidence for a superantigen in lymphocytes from HIV-discordant monozygotic twins

Response of lympho-monocytes to phytohemagglutinin in urban workers

The aim of this study is to evaluate whether traffic police exposed to urban pollutants could be at risk of changes on proliferative response of blood lympho-monocytes to the mitogen phytohemagglutinin (PHA) compared to a control group. Traffic police were matched with controls by sex, age, length of service, drinking habits and smoking habits after excluding main confounding factors. So, 77 traffic police exposed to urban pollutants (43 men and 34 women) and 77 controls with indoor activity (43 men and 34 women) were included in the study. The proliferative response of blood lympho-monocytes to the mitogen PHA was significantly lower in male and female traffic police compared to controls (respectively, P=0.000 and 0.014). The possibility of an effect on immune system and therefore on the blood lympho-monocytes proliferative answer in traffic police exposed to urban pollutants, can be assumed.

Evolutionary stable strategy: a test for theories of retroviral pathology which are based upon the concept of molecular mimicry

The genetic makeup of animal and plant populations is determined by established principles and concepts. Ecology and evolution provide a basic theoretical framework for understanding how genetic changes occur in populations. Whether these rules can be applied to host retroviral populations is unknown. Individuals infected with the human immunodeficiency virus (HIV) contain within their bodies a viral population. This population is known as a viral quasispecies. Located in the transmembrane protein of HIV-1 is the viral sequence Gly-Thr-Asp-Arg-Val. Previous immunological studies have shown that viral antibody is produced in response to this five-amino-acid sequence. Antibody to this viral sequence also crossreacts and binds to a related peptide sequence found on certain immune cells. This related sequence, Gly-Thr-Glu-Arg-Val, is found on immune cells bearing a structure known as the major histocompatibility complex (MHC). The viral transmembrane sequence, Gly-Thr-Asp-Arg-Val, can be substituted with alanine residues utilizing site-directed mutagenesis. This creates a viral clone devoid of the genetic similarity with the MHC. Chimpanzees progressing to AIDS contain both sequences of interest. Suppression of the chimpanzee quasispecies utilizing anti-retroviral drugs is proposed. This action serves to suppress the presence of the viruses containing the sequence Gly-Thr-Asp-Arg-Val. When viral load has been reduced significantly, a drug resistant, alanine altered clone is to be introduced in large numbers. The concept of evolutionary stable strategy predicts that a viable HIV clone with alanine residues can genetically dominate the viral population. Immune system recognition of the alanine sequence is likely to result in renewed antibody production. Antibodies to the alanine containing viral sequence should not recognize or bind to the MHC. Immunological parameters can then be measured to determine the physiological impact of eliminating a sequence responsible for molecular mimicry between virus and host.

The role of host immune responses in determining the outcome of HIV infection

The progression of disease following infection with human immunodeficiency virus (HIV) correlates with an activated immune system and would appear to depend to some degree on the immunogenetics of the host. Here, Michael Westby, Fabrizio Manca and Angus Dalgleish discuss the evidence for HLA determination of clinical outcome and the potential implications of a restricted T-cell receptor repertoire for pathogenesis.

Rhodamine 123: a useful probe for monitoring T cell activation

The T cell activation pathway involves an increase in mitochondrial activity. This can be evaluated in individual cells using the fluorescent probe rhodamine 123 (Rh123) and flow cytometry. Peripheral blood mononuclear cells (PBMC) were stimulated with optimal concentrations of phytohaemagglutinin (PHA), superantigens (Sag) SEA and SEC2, and allogeneic cells. Activation kinetics were followed at days 1, 2, 4 and 7. In all activation conditions, Rh123 uptake was augmented with the CD25 expression, cell size, and DNA synthesis. Rh123 uptake reflected an increase in mitochondrial activity and mass, as assessed by experiments in which Rh123 was substituted for by the 10-nonyl acridine orange, which stains mitochondria in an energy-independent manner. The spectral characteristics of Rh123 allowed us to double stain cells with Rh123 and phycoerythrin-conjugated monoclonal antibodies. In PHA-activated cultures, CD4+ and CD8+ cells incorporated essentially the same amount of Rh123 at all time points, suggesting that the two subsets did not differ in their activation kinetics. Accordingly, after 1 week of culture, no significant modification in the CD4/CD8 ratio was observed. Sag-activated CD4+ cells incorporated a higher amount of Rh123 than did CD8+ cells and preferentially expanded after 1 week of culture as indicated by the increase in the CD4/CD8 ratio. The different behavior of the CD4 and CD8 subsets observed by dual color flow cytometry in the PHA and Sag models was confirmed using purified CD4+ and CD8+ cell preparations obtained by immunomagnetic sorting. CD4+ cells were also the preferential target in the allogeneic model, although the magnitude of the phenomenon was lower than in the Sag model. Present data indicate that Rh123 is a reliable marker for monitoring the mitochondrial compartment during T cell activation. The possibility of phenotyping Rh123-stained cells adds to the applicability of the probe.