The relationship of HLA antigens to doxycycline induced apoptosis in immortalized B cells

Previous studies have shown two subsets of Lyme disease (LD) patients: a seropositive group with a high frequency of the HLA class II antigen, HLA-DR7 (DR7+), and a seronegative group with a low frequency of HLA-DR7 (DR7-). The present study examined the hypothesis that the absence or presence of this antigen may play a role in the mode of B cell death induced by doxycycline. B cells, obtained from one HLA-DR7- (AL7N) and one HLA-DR7+ (MM7P) normal volunteers, were immortalized using Epstein-Barr Virus (EBV). Doxycycline resulted in a dose-dependent decrease in cell viability which was not different between the two cell lines. DNA from the MM7P showed a strong internucleosomal fragmentation pattern consistent with apoptosis, while the AL7N showed a weaker pattern, when treated with doxycycline, 20 ug/ml, for 16 hours, a result confirmed with the TUNEL assay. In the MM7P, the level of inducible p53 peaked at 8 hours while no changes were observed in the AL7N. A much higher level of HLA class II and HLA-DR was observed in the AL7N cell line which was not affected by doxycycline. These results support the conclusion that doxycycline induces p53-dependent apoptosis in MM7P. Although doxycycline induces death in AL7N, the mode and mechanism require further study.