Background:  Apoptosis plays a major role for lymphocyte depletion in HIV⁺ patients, although mechanisms are still unclear. ART controls viral replication and leads to partial immune restoration, thus indirectly interfering with apoptosis. Studies on apoptosis examining sequential lymph nodes are rare. Here, the influence of ART on viral, immune, and apoptosis-related markers in lymph nodes of HIV⁺ individuals at initiation and after follow-up of ART has been investigated.

Methods:  Lymph nodes from 35 ART-naïve HIV⁺ patients were excised. A second lymph node excision was made under ART between 14 to 19 months later. As control, 5 lymph nodes were obtained from HIV^­ individuals. Paraffin sections were made and immunohistochemically stained with a panel of antibodies including p24, CD8, CD21, IL-7aR, Fas, FasL, Flip, bcl-2, and active caspase-3. Quantification was done by computer-assisted image analysis using the Openlab program. For statistical analysis the Wilcoxon signed rank test was used, p <0.05 was considered significant.

Results:  Generally, the number of germinal centers decreased and normalization of hyperplasia occurred under ART. In 7 of 21 patients under ART, p24 disappeared. The number of follicular and interfollicular CD8⁺ T cells decreased in 16 of 17 patients (p = 0.0004) and the CD21⁺ follicular dendritic cells (FCD) increased in 12 of 13 patients (p = 0.006) under ART. IL-7aR, which is essential for optimal cytotoxic T lymphocyte (CTL) activity, increased in 14 of 17 patients (p = 0.02). Among the apoptosis-related markers, bcl-2 in the mantel zone (16 of 17; p = 0.0004) and active caspase-3 (15 of 17; p = 0.0006) in the sinus were significantly increased, while FasL (11 of 18) interfollicularly and Fas (8 of 13) in the germinal centers increased, but did not reach statistical significance. Anti-apoptotic Flip expression was unaffected by ART.

Conclusions:  Under ART normalization of follicular hyperplasia of germinal centers, reduction of the CD8 T-cell number and recovery of FDC indicate a return to normal immune activation in lymph node similar to that in HIV^­ individuals. The increase of the IL-7aR indicates that interleukin -7 (IL-7), known to impair cell mediated immunity, is down-regulated. Reduced dysregulation of apoptosis is manifest by the up-regulation of bcl-2 in the mantle zone, of caspase-3 in the sinus, of Fas within germinal centers and of FasL interfollicularly. Hence, the highly activated immune response and the CD8 CTL-activity present in lymph nodes of untreated patients tend to normalize under ART.