Lymphocyte subpopulation number and function in infancy

Perinatal stress influences lymphocyte subset counts in neonates. The generation R study

In the general population, it is unknown whether stress-related perinatal factors influence lymphocyte subset counts in neonates. The aim of this study was to assess the associations of perinatal factors related to stress and hypoxia (mode of delivery, Apgar scores, and umbilical cord blood pH) with absolute lymphocyte subset counts (T, B, NK, helper T, cytotoxic T, naïve, memory T) in cord blood of 571 neonates. This study was embedded in a population-based prospective cohort study from fetal life onwards. All models were adjusted for gestational age, birth weight, gender, maternal fever, and each of the other perinatal stress-relating factors. Our results showed that increasing stress-related mode of delivery was positively associated with NK and memory T-lymphocyte subset counts (all p < 0.01). Effects of Apgar scores on lymphocyte subsets were explained by umbilical cord blood pH. Lower umbilical cord blood pH was associated with higher B, NK, and memory T-lymphocyte counts (all p < 0.05). Effects of mode of delivery and umbilical cord blood pH on other lymphocyte subsets were not observed. We conclude that, in the general population, lymphocyte subset counts in neonates increase with increasing stress- and hypoxia-related perinatal factors.

Hematologic and immunophenotypic factors associated with development of Rhodococcus equi pneumonia of foals at equine breeding farms with endemic infection

Rhodococcus equi causes severe pyogranulomatous pneumonia in foals and in immunocompromised people. In mice, both CD4+ and CD8+ T lymphocytes contribute to host defense against R. equi, but CD4+ T lymphocytes are required for pulmonary clearance of the bacteria. In this prospective study of 208 foals at two equine breeding farms with endemic R. equi infections, we collected peripheral blood samples at 2 and 4 weeks of age and at the time of diagnosis of R. equi pneumonia. Samples were analyzed for concentrations of total and differential leukocytes, EqCD4+ and EqCD8+ T lymphocytes, and B lymphocytes. Thirty (14.4%) foals developed R. equi pneumonia. At the 2nd week of life, affected foals had significantly lower concentrations of white blood cells (WBC) and segmented neutrophils, significantly lower proportions of EqCD4+ T lymphocytes, and significantly higher proportions of EqCD8+ T lymphocytes. The EqCD4:EqCD8 ratio was significantly lower for affected foals. At the 4th week of life, affected foals had significantly lower concentrations of segmented neutrophils and EqCD4+ T lymphocytes than did unaffected foals. The ratio of EqCD4:EqCD8 was significantly lower for affected foals. Two- and 4-week-old foals with ratios of EqCD4:EqCD8<3 were significantly more likely to develop R. equi pneumonia. There was a significant farm effect which diluted our statistical power to detect differences; however; after adjusting for the farm effect, 2-week-old foals with ratios of EqCD4:EqCD8<3 remained significantly more likely to develop R. equi pneumonia. There were no significant differences in immunophenotypic variables between affected foals (at the time of diagnosis) and age-matched control foals. These data suggest that there are hematologic and immunophenotypic differences between affected and unaffected foals during the first 2-4 weeks of life, prior to onset of clinical signs of R. equi pneumonia. These differences may represent important immunologic mechanisms associated with increased susceptibility of individual foals to infection with R. equi. Because there was considerable overlap between values for affected and unaffected foals, we cannot yet recommend immunophenotyping of foals at endemically-infected farms as a clinically useful screening tool to identify foals at increased risk of developing R. equi pneumonia.

Developmental immunology: clinical application to allergy-immunology

BACKGROUND

An increase in prevalence of allergic diseases has been seen at an unprecedented rate in many countries throughout the world. Associated with this increase in allergic disease has been a disturbing increase in morbidity and mortality of such diseases as asthma despite the availability of several new therapeutic agents over the past 2 to 3 decades. The search for both environmental factors, eg, new allergens, as well as biologic markers of genetic susceptibility, eg, respiratory viruses, has yielded considerable promise for an explanation for this rising prevalence of allergic disease.

OBJECTIVE

To present a central unifying hypothesis based upon recent knowledge concerning the developing human immune system and its interaction with external environmental factors, particularly viral infections, as a basis for a clearer understanding of the changing faces of the allergic diseases throughout the lifespan of the individual.

DATA SOURCES

English language articles were selected from PubMed, as well as selected abstracts that would have immediate, practical clinical implications.

RESULTS

Review of the current literature strongly suggests a relationship between delayed acquisition of Th1 function in the allergy-prone infant, not only as a predictive marker of susceptibility to the development of allergic disease but also as an explanation for the unique vulnerability of these infants to viral infection, eg, bronchiolitis. Furthermore, viral infection during early development in the allergy-prone infant appears to facilitate allergic sensitization in early infancy. This interesting triad of immune deficiency, viral infection, and atopic genetic susceptibility may provide a basis for early detection of allergic disease and may offer new intervention strategies for the prevention of allergic and infectious disease in the young infant.

Normal values of CD4 and CD8 lymphocyte subsets in healthy indian adults and the effects of sex, age, ethnicity, and smoking

BACKGROUND

Information on lymphocyte populations (T, B, and natural killer cells) and subpopulations (CD4 and CD8) in India is generally lacking. Measurement of T-cell subsets is important in India for evaluating disease stage and progression in individuals with the human immunodeficiency virus (HIV). Hence, this study was conducted to provide normal ranges of absolute and percentage values of CD4 and CD8 T-lymphocyte subsets and the ratio of CD4 to CD8 in normal Indian adults.

METHODS

Flow cytometric analysis (EPICS-XL) was used to determine the range of T-lymphocyte subpopulations in normal Indian blood donors at Command Hospital and the Armed Forces Medical College, Pune, India. The reference population consisted of 94 healthy HIV-seronegative blood donors. T-lymphocyte subsets were analyzed with two-color immunophenotyping of peripheral blood lymphocytes with the use of a lysed whole-blood technique and enumerated.

RESULTS

For normal values of various blood components, we found mean values of 2114 cells/microl for total lymphocytes, 865 cells/microl (40.2%) for CD4(+) lymphocytes, 552 cells/microl (31.3%) for CD8(+) lymphocytes, and 1.7 for the CD4:CD8 ratio. The 95% confidence intervals for the same parameters were 1115-4009 cells/microl, 430-1740 cells/microl (30.75-49.60%), 218-1396 cells/microl (20.06-42.52%), and 0.39-3.02 respectively. Females had significantly higher CD4 counts (P < 0.05), percentage of CD4 lymphocytes (P < 0.01), and CD4:CD8 ratio (P < 0.01). Males had a significantly higher percentage of CD8 lymphocytes (P < 0.01). They also had higher CD8 counts that did not reach significance. Age, ethnicity (Dravidian versus Aryan), smoking, alcohol consumption, and the interval between drawing the blood sample and its analysis were factors that did not produce statistically significant differences in the T-cell subsets studied.

CONCLUSIONS

When compared with other published series, the CD4 and CD8 values in healthy Indians were no different from those reported in the West. These observations have important clinical implications for the use of T-lymphocyte subset measurements in India, especially in the management of HIV infection. The normal ranges established by this study can be used as a reference for decisions made in clinical practice.