Limited impact of the thymus on immunological recovery during and after chemotherapy in patients with diffuse large B-cell lymphoma

The Impact of Absolute CD4 Count and Percentage Discordance on Pneumocystis Jirovecii Pneumonia Prophylaxis in HIV-Infected Patients

Current guidelines suggest that HIV-infected patients should receive chemoprophylaxis against Pneumocystis jirovecii pneumonia (PJP) if they have a cluster determinant 4 (CD4) count <200 cells/mm³ or oropharyngeal candidiasis. Persons with CD4 percentage (CD4%) below 14% should also be considered for prophylaxis. Discordance between CD4 count and CD4% occurs in 16% to 25% of HIV-infected patients. Provider compliance with current PJP prophylaxis guidelines when such discordance is present was assessed. Electronic medical records of 429 HIV-infected individuals who had CD4 count and CD4% measured at our clinic were reviewed. CD4 count and percentage discordance was seen in 57 (13%) of 429. Patients with CD4 count >200 but CD4% <14 were significantly less likely to be prescribed PJP prophylaxis compared with those who had CD4 count <200 and CD4% >14 (29% versus 86%; odds ratio = 0.064, 95% confidence interval: 0.0168-0.2436; P < .0001). We emphasize monitoring both the absolute CD4 count and percentage to appropriately guide PJP primary and secondary prophylaxis.

Thymic hyperplasia after chemotherapy in adults with mature B cell lymphoma and its influence on thymic output and CD4(+) T cells repopulation

To investigate the thymic regenerative potential in adults accepting chemotherapy for lymphoma. The dynamics of thymic activity in 54 adults from baseline to 12 mo post-chemotherapy was analyzed by assessing thymic structural changes with serial computed tomography (CT) scans, and correlating these with measurements of thymic output by concurrent analysis of single-joint (sj) T-cell receptor excision circles (sjTREC) and CD31⁺ recent thymic emigrants (RTE) in peripheral blood. Furthermore, the consequence of thymic renewal on peripheral CD4⁺ T cell recovery after chemotherapy was evaluated. Time-dependent changes of thymic size and thymic output assessed by both sjTREC levels and CD31⁺ RTE counts in peripheral blood were observed during and after chemotherapy. Enlargement of thymus over baseline following chemotherapy regarded as rebound thymic hyperplasia (TH) was identified in 20 patients aged 18−53 y (median 33 y). By general linear models repeated measure analysis, it was found that, patients with TH (n = 20) had a faster recovery of sjTREC levels and CD31⁺ RTE counts after chemotherapy than patients with comparable age, gender, diagnosis, disease stage, thymic volume and output function at baseline but without TH (n = 18) (p = 0.035, 0.047); besides, patients with TH had a faster repopulation of both naïve CD4⁺ T cell and natural regulatory CD4⁺ T cell subsets than those without TH (p = 0.042, 0.038). These data suggested that adult thymus retains the capacity of regeneration after chemotherapy, especially in young adults. The presence of TH could contribute to the renewal of thymopoiesis and the replenishment of peripheral CD4⁺ T cell pool following chemotherapy in adults.

Does discordancy between the CD4 count and CD4 percentage in HIV-positive individuals influence outcomes on highly active antiretroviral therapy?

INTRODUCTION

The CD4 count and CD4 percentage (CD4%) are both strong predictors of clinical disease progression in human immunodeficiency virus (HIV). Although individuals may show discordancy between their CD4 count and CD4%, the clinical relevance of this is unclear.

METHODS

Discordancy was defined where the CD4% was ≤10th percentile for a selected CD4 count range (referred to as low discordancy), within the central 80% range (concordant), or ≥90th percentile (high discordancy). Regression methods identified factors associated with low and high discordancy in untreated individuals and assessed the impact of discordancy on treatment responses to highly active antiretroviral therapy (HAART).

RESULTS

High discordancy was associated with female sex, low viral load, and white ethnicity; low discordancy was associated with black or nonwhite ethnicity, older age, and injection drug use. Clinical event rates were higher in individuals with high discordancy starting HAART, but there was no association with subsequent HIV progression by 6 months after starting HAART. CD4 count increases remained lower, by 20 cells/mm(3), in individuals with low discordancy, and higher, by 27 cells/mm(3), in those with high discordancy.

CONCLUSIONS

Overall discrepancies between the CD4/CD4% are small, confirming the use of absolute CD4 counts as a monitoring tool.