OBJECTIVETo explore the immuno-effect of plasmacytoid dendritic cells (pDC) on bacteria infection induced spontaneous remission (SR) of leukemia.

METHODSBoth pDC and myeloid dendritic cells (mDC) were isolated and purified from leukemic patient with SR and healthy donor by combination of immunomagnetic beads and flow cytometry. pDC were cultured in RPMI1640 medium and stimulated with different bacteria. The T cells proliferation was detected by MTT, and cytokine production by ELISA kits.

RESULTSThe human bacterial pathogen Staphylococcus aureus and Pseudomonas aeruginosa stimulation for 48 h resulted in the maturation of pDC with production of high quantity of IFN-α at (15.34 ± 2.91) ng/ml and (10.38 ± 1.41) ng/ml, respectively, comparing with that of negative group at (1.36 ± 0.13) ng/ml (P<0.01). Activated pDC could promote the differentiation of naive CD4⁺ T cells to Th1 cells with secretion of IFN-γ at (2.16 ± 0.37) ng/ml and (2.73 ± 1.11) ng/ml, respectively, comparing with that of positive control at (2.55 ± 0.23) ng/ml (P > 0.05). Activated pDC showed higher T cell stimulatory capacities [proliferation index (PI) was 4.36 and 4.05, respectively] than that of non-activated pDC (PI was 1.23 and 0.13, respectively) (P < 0.01).

CONCLUSIONStaphylococcus aureus and Pseudomonas aeruginosa activated pDC may play a key role in SR of leukemia following severe infections.