Procalcitonin as a parameter of disease severity and risk of mortality in patients with Plasmodium falciparum malaria

The serum levels of procalcitonin (PCT) in Plasmodium falciparum malaria were evaluated for clinical significance in 66 nonimmune and semi-immune patients. Of the 66 patients, 36 had uncomplicated malaria, 24 had severe and complicated malaria, and 6 had fatal malaria (5 from previous studies). Pretreatment PCT concentrations were closely correlated with parasitemia. Concentrations were lowest in semi-immune patients with uncomplicated malaria, compared with those in nonimmune patients (geometric mean concentrations [GMCs], 1.07 and 2.37 ng/mL, respectively), and were highest in severe and complicated cases (GMC, 10.67 ng/mL; P<.001 among all subgroups). Six of 7 patients with PCT concentrations >25 ng/mL died. PCT concentrations decreased on day 2 of treatment in survivors but not in patients with fatal outcome. Thus, repeated PCT measurements may provide useful prognostic information, especially in medical centers that are not experienced in parasite density determination.

CD4 alphabeta T lymphocytes express high levels of the T lymphocyte antigen CTLA-4 (CD152) in acute malaria

The role of T lymphocytes in human acute malaria remains under debate. The kinetics of T cell activation in acute malaria were investigated, with emphasis on CTLA-4 (CD152). In patients with malaria, CTLA-4 expression by CD4 alphabeta T lymphocytes was highly increased. After initiation of antiplasmodial treatment, it returned to control values within a few days. gammadelta T cells, which also are implicated in the pathogenesis of human malaria, did not express CTLA-4. The level of CTLA-4 expression at the time of hospital admission was correlated positively with other markers of disease severity-the peak of the parasitemia and the peak of serum neopterin levels. These results show that CTLA-4 is a sensitive and dynamic marker for T lymphocyte activation. Its strong increase in acute malaria argues for the involvement of T cells in the human immune response to plasmodia.

Enhanced expression of CTLA-4 (CD152) on CD4+ T cells in HIV infection

CTLA-4 (CD152) is a surface molecule of activated T cells with sequence homology to CD28. Both molecules bind to the same ligands, B7.1 (CD80) and B7.2 (CD86) but have antagonistic functions. While CD28 is an important costimulator, CTLA-4 has an essential inhibitory function in maintaining the homeostasis of the immune system. Down-regulation of CD28 predominantly on CD8+ T cells has been described in HIV infection, but analysis of CTLA-4 is complicated by its low expression levels. Here we have used potent signal enhancement to study CTLA-4 on peripheral blood mononuclear cells (PBMC) during HIV infection. CTLA-4 was expressed only on T cells. Expression levels were significantly increased selectively on CD4+ T cells during all stages of HIV infection, while CTLA-4 expression on CD8+ T cells was always low. In contrast, after stimulation with the mitogen phytohaemagglutinin (PHA), CTLA-4 levels were strongly increased on T cells from controls but in T cells from HIV patients this response was severely impaired. Our data suggest that in HIV infection CD4+ and CD8+ T cells may be less responsive to B7 costimuli due to two different mechanisms: increase in CTLA-4 expression by CD4+ cells and down-regulation of CD28 by CD8+ cells.

Oligoclonal T cell proliferation in patients with rheumatoid arthritis and their unaffected siblings

OBJECTIVE

To analyze whether patients with rheumatoid arthritis (RA) have an intrinsic defect in T cell proliferation and survival, possibly contributing to the infiltration of the synovial membrane with CD4+ T cells.

METHODS

Fifteen patients with seropositive RA, 11 patients with psoriatic arthritis, 20 normal controls, and 9 affected and 13 unaffected siblings from 7 multiplex families with RA were analyzed for clonal proliferation. To investigate this clonal T cell proliferation, CD4+ T cells were purified from peripheral blood and synovial fluid by magnetic bead separation. T cell receptor (TCR) beta-chain sequences were amplified by reverse transcriptase-polymerase chain reaction, using TCR BV and BJ gene segment-specific primer sets. Clonally expanded T cell specificities were identified by size fractionation and sequencing of the amplified product.

RESULTS

All RA patients carried clonally expanded CD4+ T cells in the peripheral blood compartment. Such expanded CD4+ T cell clonotypes were only infrequently observed both in normal individuals (P < 0.0001) and in patients with psoriatic arthritis (P = 0.004). Lymphoproliferation of selected CD4+ T cells was shared by affected and unaffected siblings from RA multiplex families (P = 0.005 and P = 0.0003, respectively, compared with normal controls). Expanded clonotypes persisted for several years and contributed to the T cell infiltrate in the joint. Clonal T cell proliferation involved a diverse spectrum of TCR molecules.

CONCLUSION

RA patients have an abnormality in the homeostasis of CD4+ T cells, characterized by the emergence of clonally proliferating populations. The presence of clonal outgrowth of selected CD4+ T cells specificities in unaffected siblings of RA patients suggests that oligoclonality of CD4+ T cells is inherited and is a risk factor for, rather than a result of, synovial inflammation.

T cell receptor germline gene segments and HLA haplotypes control the length of the CDR3 of human T cell receptor beta chains

The third complementarity determining region (CDR3) is the most variable part of alpha beta T cell receptors (TCR) and represents the putative antigen contacting site. To identify parameters determining the structural diversity of the CDR3 region, the CDR3 length distributions of 66 BV-J combinations in peripheral CD4+ T cells (6 BV and ll BJ gene segments) of 12 unrelated individuals were analyzed. The median CDR3 length ranged from 8 to 12.5 amino acids and was partially determined by the usage of the BV and BJ gene segment. Beyond the influence of germline-encoded TCR gene segments, donors expressed an individual pattern of preferred CDR3 size classes. To identify mechanisms determining this individual pattern, 17 first-degree relatives from five families were studied. CDR3 length profiles were shared by some but not all relatives. Sharing of CDR3 length profiles correlated with the inheritance of both HLA-DR haplotypes. These data suggest that the length of the TCR beta chain is selected and that restrictions on the diversity of the CDR3 length are imposed by germline-encoded TCR gene segments as well as by major histocompatibility complex-dependent mechanisms.

Heterogeneity of tumour necrosis factor production in renal cell carcinoma

Endogenous tumour necrosis factor (TNF) production was investigated by in situ hybridisation and immunohistochemistry in 8 renal cell carcinoma (RCC) patients at different stages of disease. Analysis of frozen sections of tumour biopsy specimens revealed variable degrees of macrophage infiltration and great heterogeneity in TNF gene expression. Two metastatic tumours investigated showed abundant TNF protein production and marked macrophage infiltration. Based on morphological criteria, these TNF-positive cells most likely belong to the macrophage lineage. Two years after nephrectomy the individual survival time was recorded; however, the small numbers did not yet allow any correlation of TNF production to the clinical course of disease. Further studies will be required to eventually reveal the role of TNF in renal cell carcinoma development.

Regulation of tumor necrosis factor gene expression in colorectal adenocarcinoma: in vivo analysis by in situ hybridization

Tumor necrosis factor (TNF) produced by macrophages is thought to contribute to the host defense against development of cancer. However, since tumor cells themselves are able to produce TNF, it is conceivable that TNF may also play an adverse pathological role in carcinogenesis. To better understand the functional significance of TNF in neoplastic disease, we have determined the cellular source of TNF activity produced in 10 patients with colorectal cancer. Northern blot analysis of RNAs extracted from fresh biopsy specimens revealed detectable TNF mRNA levels in all instances. By using in situ hybridization of frozen sections, scattered cells expressing TNF mRNA could be discerned. Based on morphological criteria, these TNF-positive cells most likely belong to the macrophage lineage. Macrophages in normal tissue surrounding the tumor did not express TNF mRNA, suggesting that macrophage activation occurs locally at the site of neoplastic transformation. Immunohistochemistry using anti-TNF monoclonal antibodies revealed that less than 1% of tumor-infiltrating macrophages synthesize TNF protein. Thus we present evidence that in colorectal cancer only a small proportion of tumor-infiltrating macrophages produces TNF, indicating that the microenvironment of the tumor provides adequate, yet suboptimal, conditions for macrophage activation.

IL-2 production in human T lymphotropic virus I-infected leukemic T lymphocytes analyzed by in situ hybridization

In situ hybridization studies were performed with 35S-labeled anti-sense RNA probes to study IL-2 mRNA expression in three human T lymphotropic virus I-infected T cell lines at the single cell level. In HuT 102, MT-2, and MT-4 cells, IL-2 mRNA-expressing cells were identified, occurring at frequencies of 2 x 10(-2), 8 x 10(-3), and 5 x 10(-3), respectively. In these cell lines, IL-2 mRNA was not detectable in RNA extracted from whole adult T cell leukemia cell populations because of dilution by other RNA species from the vast majority of cells that do not contain IL-2 mRNA. The data indicate the possibility of paracrine growth stimulation via IL-2 and its receptor even in those human T lymphotropic virus I-infected T cell populations that apparently lack IL-2 activity when analyzed by conventional assay procedures.

IL-2 production in human T lymphotropic virus I-infected leukemic T lymphocytes analyzed by in situ hybridization

In situ hybridization studies were performed with 35S-labeled anti-sense RNA probes to study IL-2 mRNA expression in three human T lymphotropic virus I-infected T cell lines at the single cell level. In HuT 102, MT-2, and MT-4 cells, IL-2 mRNA-expressing cells were identified, occurring at frequencies of 2 x 10(-2), 8 x 10(-3), and 5 x 10(-3), respectively. In these cell lines, IL-2 mRNA was not detectable in RNA extracted from whole adult T cell leukemia cell populations because of dilution by other RNA species from the vast majority of cells that do not contain IL-2 mRNA. The data indicate the possibility of paracrine growth stimulation via IL-2 and its receptor even in those human T lymphotropic virus I-infected T cell populations that apparently lack IL-2 activity when analyzed by conventional assay procedures.

T cell subpopulations in inflammatory bowel disease: evidence for a defective induction of T8+ suppressor/cytotoxic T lymphocytes

Abnormal immune responses associated with inflammatory bowel disease may reflect a defect in immunoregulatory functions. To analyse T-T cell cooperation, we examined the influence of polyclonal activation with the mitogen phytohaemagglutinin on the distribution of the T4+ helper/inducer and the T8+ cytotoxic/suppressor T cell subset. Compared to controls, lymphocytes from patients with Crohn's disease displayed a slight reduction in T3+ cells; neither in patients with ulcerative colitis nor in patients with Crohn's disease a significant difference in T4+ and T8+ cells and the T4/T8 ratio was observed. Phytohaemagglutinin stimulation of normal lymphocytes resulted in a decrease of the T4 subset and a clear increase of the T8 subpopulation. In contrast, the subset distribution pattern was not changed by the mitogenic stimulation in any of the patients. This abnormal reaction pattern could not be influenced by the addition of interleukin-2. Small numbers of normal lymphocytes, however, were able to restore the predominant proliferation of T8+ cells. Thus, the reduced response of T8+ lymphocytes cannot be attributed to an altered composition of this subset in patient with inflammatory bowel disease; our results provide evidence for a defective induction of T8+ suppressor/cytotoxic T cells, which is independent from disease activity.