Lymphocyte depletion during treatment with intensive chemotherapy for cancer

Recently we have observed an increased incidence of opportunistic infections in patients treated with intensive chemotherapy for cancer. Because T-cell depletion is associated with similar clinical events in human immunodeficiency virus infection and after bone marrow transplantation, we have analyzed peripheral blood lymphocyte populations in a series of patients during treatment with intensive chemotherapy for cancer. Although neutrophil, monocyte, and platelet numbers consistently recovered to greater than 50% of pretreatment values after each sequential cycle of therapy, lymphocyte numbers did not recover within the same time period. B cells decreased rapidly from a mean value of 149 +/- 46/mm3 before chemotherapy to 4 +/- 1/mm3 during chemotherapy (P = .01). CD4+ T cells decreased from a mean of 588 +/- 76/mm3 before chemotherapy to 105 +/- 28/mm3 during chemotherapy (P = .0002) and CD8+ T cells decreased from a mean of 382 +/- 41/mm3 before chemotherapy to 150 +/- 46/mm3 during chemotherapy (P = .0009). Natural killer cell numbers did not show significant declines (171 +/- 30/mm3 before, 114 +/- 24/mm3 during, P = .19). Based on the history of opportunistic complications in patients with other disorders who display similar degrees of CD4+ T-cell lymphopenia and preliminary observations in this population, immune incompetence could surface as a dose-limiting toxicity for highly dose-intensive chemotherapy regimens.     

Early functional effects of Clostridium difficile toxin A on human colonocytes

BACKGROUND & AIMS: Previous in vitro studies have shown that Clostridium difficile toxin A is able to directly affect the intestinal epithelial barrier function. The aim of this study was to examine the early effects of toxin A on mucin exocytosis and determine whether this toxin can induce the production of the chemokine interleukin 8 (IL-8) from human colonic epithelial cells. METHODS: Two model systems were used: the HT29-CI.16E colonic goblet cell line and primary cultures of human normal colonocytes. RESULTS: Toxin A exerted a rapid and dose- related inhibition of stimulated mucin exocytosis without altering baseline (constitutive) mucin exocytosis from HT29-CI.16E cells. Toxin A was also able to induce the secretion of IL-8 from both HT29-CI.16E cells and primary cultures of human normal colonocytes, as early as 2-3 hours of incubation. CONCLUSIONS: The results show that while toxin A is able to down-regulate stimulated mucin exocytosis, it is able to up- regulate the secretion of an important chemoattractant chemokine, IL-8. These modifications illustrate the ability of colonocytes to recruit inflammatory and immune cells that will eventually bring about major mucosal damage. (Gastroenterology 1997 Jun;112(6):1887-94)     

Limiting-dilution analysis of the effects of colony-stimulating factors, phytohemagglutinin, and hydrocortisone on hematopoietic progenitor cell growth

The effects of colony-stimulating factors (CSFs), phytohemagglutinin (PHA), and hydrocortisone on the growth of human bone marrow hematopoietic progenitor cells (granulocyte-macrophage; GM) were analyzed in a limiting-dilution assay (LDA). Both low-density bone marrow cells separated by discontinuous Percoll gradients and a T cell- depleted and progenitor-enriched cell fraction obtained by the combination of counterflow elutriation centrifugation and Percoll gradients were examined in LDA. GCT (monocytoid cell line-conditioned medium containing GM-CSF), human placenta-conditioned medium, bladder carcinoma cell line 5637-conditioned medium (containing GM- and G-CSF), and recombinant CSF (G-CSF) directly induced proliferation of progenitors with single-hit kinetics. In some instances, however, PHA- stimulated lymphocyte-conditioned medium (containing G- and GM-CSF) showed deviation from single-hit kinetics, which demonstrated the presence of factor(s) suppressive to progenitor growth. In a T cell- depleted, progenitor-enriched fraction, PHA alone was found to suppress progenitor growth at a level as low as 100 ng/mL. The addition of hydrocortisone (10(-6) mol/L) increased the progenitor frequency but suppressed progenitor growth at 10(-4) mol/L. LDA appears to be a valuable method for exploring mechanisms of factors regulating hematopoietic cell growth.     

Role of exercise evaluation in restrictive lung disease: new insights between March 2001 and February 2003

Restrictive lung disease is often first detected when patients complain of dyspnea on exertion. Many forms of exercise testing are available, from simple hallway oximetry to the more formal and more complex cardiopulmonary exercise test. Although the use of exercise for diagnosis, treatment, and predicting outcomes is largely understudied in this population, it has recently been shown to be of value in some settings. Exercise testing may be a valuable diagnostic tool in determining the extent of lung disease in sarcoidosis. Medinger et al. reported that the symptom-limited exercise test detected pulmonary dysfunction earlier than history, physical examination, chest radiography, and spirometry alone. Furthermore, Delobbe et al. noted that in patients with biopsy-proved sarcoidosis, cardiopulmonary exercise testing was a more sensitive indicator of early lung disease than pulmonary function tests. The American College of Chest Physicians/American Thoracic Society have published an updated consensus statement for cardiopulmonary exercise testing. Christensen et al. reported that patients with restrictive lung disease may be at risk for hypoxemia with light exercise while on an airplane, and suggest that these patients be considered for in-flight oxygen therapy. Lastly, Herridge and the Canadian Critical Care Trial Group used the 6-minute walk test to prove that survivors of acute respiratory distress syndrome have significant functional limitation 1 year after discharge from the intensive care unit largely secondary to neuromuscular sequelae. Exercise testing appears to be a valuable tool in evaluating, treating, and predicting outcomes in patients with restrictive lung disease. Further study will help to support its use in other restrictive lung diseases.     

Characterization of immature T cell subpopulations in neonatal blood

A series of monoclonal antibodies directed against T cell differentiation antigens was used to identify circulating T cells in normal human neonates. Twenty-five cord blood samples, taken after cesarean or vaginal delivery, and 16 venous blood samples from normal adult controls were examined using monoclonal antibodies in an indirect immunofluorescence technique. The percentage of circulating OKT3 positive (pan-T cell) cells was significantly lower in the neonatal blood (52.8%) compared with the adult controls (74.9%) (P less than .001). Of the cord mononuclear cells, 58% showed reactivity with OKT10 (common thymocyte antigen) compared with only 7% in adult controls (P less than .001). The helper:suppressor T cell ratio was lower in cord blood (1:2) as compared with 1:3 for adult blood (P less than .005) as observed in these studies. These figures reflect the presence of a significant population (25%) of immature T cells in cord blood that expresses simultaneously both helper (OKT4) and suppressor (OKT8) phenotypes. Twenty-four percent of the T cells in cord blood also expressed OKT6 antigen (cortical thymocyte), a feature not found in adult blood. Double-labeling studies characterized a previously undescribed blood T cell phenotype, which was simultaneously OKT6 and OKT3 (pan-T cell) positive; of the cells reactive with OKT3, 43% also were positive with OKT6. This study reveals the presence of immature populations of T cells in normal human neonatal blood exhibiting phenotypes characteristic of normal developing thymocytes and a previously undescribed cell phenotype.     

Nucleoside transport and proliferative rate in human thymocytes and lymphocytes

The thymus is a site of active T-lymphoid cell proliferation and DNA synthesis. In this study, the capacity of human thymocytes for nucleoside transport was assessed both by cytosine arabinoside influx and by equilibrium binding of nitrobenzylmercaptopurine riboside (NBMPR), a specific ligand for the equilibrative nucleoside transporter of leukocytes. The proportion of freshly isolated thymocytes synthesizing DNA was 8.6% +/- 2.1% (n = 12) by 3H-thymidine labeling index and 7.8% +/- 2.9% (n = 4) S-phase cells by flow cytometric analysis of DNA content. In comparison, both methods gave proliferation S-phase values less than 1% for peripheral blood lymphocytes (PBLs). Thymocytes expressed a high density of specific NBMPR binding sites (26,068 +/- 8,776 sites per cell, n = 12) as compared with PBLs (1,123 +/- 553 sites per cell, n = 8). The initial influx of cytosine arabinoside into thymocytes was 14-fold greater than into PBLs, and in both cell types the influx of nucleoside was totally inhibited by 0.5 mumol/L NBMPR, which is known to inhibit the major equilibrative nucleoside transporter in white blood cells. Depletion of mature CD3+ cells from the thymocyte preparation by anti-CD3 antibody left a residual population with both increased labeling index and up to twofold greater density of NBMPR binding sites. When PBLs were cultured for 48 hours with the T-cell mitogen phytohemagglutinin, a 40-fold increase in labeling index was observed, together with a 30-fold increase in the density of specific NBMPR binding sites. Thus, fresh thymocytes from human thymus are actively proliferating and express high densities of a functional nucleoside transporter. The more immature cells in the thymocyte population which are proliferating more actively have a greater density of nucleoside transporters than the whole population. In contrast, mitotically inactive PBLs-have few nucleoside transporters, but after mitogenic stimulation PBLs express large numbers of this transmembrane molecule.