Temporal variability in immunological parameters: Peripheral blood mononuclear cell subsets, serum immunoglobulins, and soluble markers of immune system activation

Variability of CD4+ Cell Counts in HIV-1-Uninfected Volunteers Who Are Eligible for a Phase I HIV Vaccine Study

OBJECTIVE

Vaccines and biologics containing CD4 molecules or HIV-1 gp120 might induce antibodies targeting CD4. We evaluated temporal variability of CD4 levels in healthy volunteers to quantify declines that could indicate true adverse events.

DESIGN

Prospective observational cohort study of 100 healthy adults without HIV-1 infection from the Baltimore region.

METHODS

Participants enrolled and consented to blood draws for immunologic laboratory panels performed once every 8 weeks for 48 weeks. The primary CD4 measurements were CD4 absolute count (cells/mm) and CD4 percentage (CD4%, total CD4 cells/total lymphocyte cells). CD4 changes over time were modeled using fold changes for CD4 absolute counts and differences for CD4 percentages.

RESULTS

Variation of average CD4 cell counts and percentages were highly participant-specific (P < 0.001 for both). However, changes in both CD4 measurements over time were stable in the population. We proposed thresholds to flag unusual drops using 1.5 SD estimates, calculated as 1.5-fold declines for CD4 count and 6.4% declines for CD4 percentage. In this healthy cohort, flagging simultaneous declines in both measurements corresponded to a low false-positive rate (5.26%).

CONCLUSIONS

Normal biological variation in large lymphocytes should be taken into account to establish thresholds for adverse changes in clinical trials. The inherent subject-specific variability in CD4 levels makes establishing absolute cutoffs difficult. However, this study proposes that thresholds for declines using 1.5 SDs from these data (50% in absolute count and 6.4% for CD4 percentage) allow a small false-positive rate (∼5%) that could maintain sensitivity for true adverse events in a clinical trial.

Mid-life stress is associated with both up- and down-regulation of markers of humoral and cellular immunity

Perception of stress with consequent activation of a neuroendocrine cascade causes changes in immune function that may be bi-directional, with alterations in basal levels of biological parameters outside the optimal range. In this cross-sectional study of 302 healthy persons (males 56.3%, females 43.7%) aged 41-46 years, higher stress levels, as assessed by questionnaire measures of recurrent and recent perceived stress, were associated with a 4-fold greater risk of having a high compared to mid-range serum neopterin concentration, indicating activation of cellular immune mechanisms [adjusted odds ratio, OR; (95% confidence intervals, CI): Low stress=1.00 (reference group); Medium stress=4.13 (1.51, 11.29); High stress=4.63, (1.35, 15.83), p for trend=0.01]. Higher stress levels were associated with a 3-fold greater risk of having signs of humoral immune activation, as indicated by salivary IgA concentration [high compared to mid-range salivary IgA: Low stress=1.00 (reference group); Medium stress=1.06 (0.48, 2.34); High stress=3.62 (1.26, 10.39), p for trend=0.02], but also a 4-fold greater risk of humoral immune depression [low compared to mid-range IgA: Low stress=1.00 (reference group); Medium stress=1.72 (0.74, 3.99); High stress=4.38 (1.47, 13.00), p for trend=0.02]. In conclusion, in this cross-sectional study, higher stress levels were associated with higher serum neopterin and both elevated and depressed salivary IgA levels. These findings emphasise the importance of considering that stress may have bi-directional effects on immune mechanisms, and are consistent with an activational effect of chronic, perceived stress on cellular immunity, and a bi-directional effect on IgA levels, one aspect of humoral immunity.

Effects of symptomatic severity on elevation of plasma soluble interleukin-2 receptor in bipolar mania

BACKGROUND

Circulating soluble interleukin-2 receptors (sIL-2Rs) and soluble interleukin-6 receptors (sIL-6Rs) are stable immune measures. Elevated plasma sIL-2R levels are present in patients with schizophrenia, major depression, and bipolar mania, but not with minor psychiatric disorders. The increased plasma sIL-2R levels are state-dependent in bipolar mania. However, altered production of plasma sIL-6R and the effects of clinical characteristics on plasma sIL-6R and sIL-2R levels in bipolar disorder remains uncertain.

METHODS

Plasma sIL-2R and sIL-6R levels were measured in 31 Taiwanese bipolar manic (DSM-IV) patients with Young Mania Rating Scale (YMRS) scores of > or =26 as well as during the subsequent remission (YMRS< or =12), and equal numbers of age- and gender-matched healthy controls. The relationships of clinical variables such as age, age of onset, smoking, medication status, coexisting psychotic features, number of prior episodes, duration of illness, presence of depression before or following the manic episode, and manic severity to plasma sIL-2R and sIL-6R levels in acute mania along with remission were examined.

RESULTS

Plasma sIL-2R but not sIL-6R levels were significantly higher in acute mania than in subsequent remission (P<0.05) and controls (P<0.0005). In acute mania, the plasma sIL-2R levels were significantly correlated to YMRS scores (r=0.34, P<0.05). The remaining clinical variables had no effect on plasma sIL-2R and sIL-6R levels in acute mania or remission. There was a significantly positive relationship between the reduction of plasma sIL-2R levels from the acute to follow-up measurements (DeltasIL-2R) and symptomatic improvement of acute mania (DeltaYMRS) (r=0.61, P<0.001).

LIMITATIONS

Our sample included medicated and unmedicated patients in acute mania. The psychotropic medication may have divergent effects on the plasma sIL-2R levels in acute mania and subsequent remission.

CONCLUSIONS

Elevation of plasma sIL-2R but not sIL-6R levels in bipolar mania supports the idea that the immunomodulatory mechanism may vary in different psychotic disorders. In contrast to being a trait marker in schizophrenia and depressive disorder, plasma sIL-2R levels may be considered a biological indicator of manic severity in a group of bipolar affective patients.

Measurement of cytokines in clinical samples using immunoassays: problems and pitfalls

With the explosion in interest in cytokines and an increasing understanding of their possible involvement in the pathogenesis of many diseases, the number of studies measuring cytokines in body fluids has increased markedly over the last 5 to 10 years. However, it is readily apparent from the literature that the level of awareness of the many factors that can potentially influence the results obtained is very low. Such factors are likely to contribute considerably to the disparities seen among similar types of study. These include assay properties such as standardization and specificity, type of sample and sample handling, and many biological influences such as age, sex, ethnic background, and diurnal rhythmicity. Clearly, it is not possible to control for all these factors, but a minimum evaluation of assays should be carried out as described, including recovery and parallelity studies using relevant samples and the establishment of reproducibility and normal healthy population levels. An awareness of these factors, which is the purpose of this review, may hopefully lead to an improvement in the quality of studies incorporating the measurement of cytokines in clinical samples and should aid in the interpretation of the data.

Neopterin: a review

Neopterin was discovered in bee larvae, in worker bees and in royal jelly. The compound was termed "neopterin" to denote that it might start a new (Greek, neo) epoch in pteridine research. Increased concentrations of neopterin were reported in patients with viral infections, suggesting that increased neopterin may originate from the immune response of patients to the infections. In vitro studies revealed that human monocytes/macrophages produce neopterin when stimulated by interferon-gamma. Neopterin can easily be detected in serum and urine. The most important clinical applications for the determination of neopterin are prognostic indicator of malignant diseases, follow-up control of chronic infections, monitoring of immune-stimulatory therapy, differential diagnosis of acute viral and bacterial infections, prognostic indicator in HIV infections and early indications of complications in allograft recipients. In recent years new physiological functions of neopterin have been discovered such as inducing or enhancing cytotoxicity, inducing apoptosis and the role of a chain breaking antioxidant. This review will focus on the immunological and physiological properties of neopterin.

Immune consequences of stroke and cerebral palsy in adults

The possibility that brain damage results in a sustained dysregulation of lymphocyte responsiveness to the lymphokine, interleukin-2 (IL-2), was investigated in individuals who had experienced a unilateral stroke in adulthood or who presented with spastic hemiparesis since childhood. Following verification of unilateral brain damage via neuromotor assessment, and determination of their health status, blood samples were obtained to evaluate a panel of immune measures. Soluble interleukin-2 receptor (sIL-2R) and lymphocyte proliferative and cytolytic responses in the subjects with stroke or cerebral palsy were compared to age- and gender-matched controls. In addition, lymphocyte populations were enumerated via flow cytometry, and lymphocyte cyclic AMP (cAMP) levels were determined. Circulating blood levels of sIL-2R were significantly elevated in all individuals that had experienced unilateral brain damage. Cytolytic activity also failed to be stimulated to the normal level by in vitro treatment of lymphocytes with IL-2. Further, lymphocytes from the stroke subjects proliferated significantly less after mitogen and IL-2 stimulation. These functional differences were not accounted for by an abnormal leukocyte profile, although phenotypic analyses revealed subtle differences in the natural killer cell subsets. Overall, the findings indicate that individuals with brain damage may not respond appropriately when immune activation is required. These immune differences appear to be a stable trait given that they were manifested after both perinatal and adult brain insult in otherwise healthy, independently living individuals.