[Expression of CD16zeta in NK cells of B-cell non-Hodgkin's lymphoma patients and in vitro killing effect of rituximab combined lymphokine-activated killer cells on B-NHL cells].

BACKGROUND & OBJECTIVE: Natural killer (NK) cells are the main effector of antibody-dependent cellular cytotoxicity (ADCC). The activation disorder of NK cells in cancer patients may affect the treatment effect of monoclonal antibody. Reversing the dysfunction of signal transduction of CD16zeta chain in NK cells and combining lymphokine-activated killer (LAK) cells with rituximab may give rise to synergistic effect. This study was to find out whether the activation disorder of NK cells exist in B-cell non-Hodgkin's lymphoma (B-NHL) patients, whether interleukin-2 (IL-2) can reverse the activation disorder in vitro, and whether the combination of rituximab and LAK cells can produce synergistic antitumor effect.

METHODS

Peripheral blood mononuclear cells (PBMCs) were isolated from 69 B-NHL patients and 30 healthy donors by density gradient centrifugation method, and cultured with IL-2 (1 000 U/ml) to prepare LAK cells. The positive rate and median fluorescence intensity (MFI) of CD16zeta chain in PBMCs and LAK cells were detected by flow cytometry (FCM). The expression of CD20 on Raji cells was also detected by FCM. The apoptosis of Raji cells after treatment of rituximab was detected by FCM with Annexin V/PI staining. The cytotoxicity was assessed by lactate dehydrogenase (LDH) release experiment.

RESULTS

The positive rate and MFI value of CD16zeta chain on CD56+ cells were significantly lower in B-NHL group than in control group [(63.3+/-16.4)% vs. (97.8+/-3.1)%, P<0.001; 1.3+/-1.3 vs. 3.6+/-1.7, P<0.001]. There was no significant difference in the positive rate and MFI value of CD16zeta on LAK cells between the 2 groups [(99.3+/-4.1)% vs. (99.7+/-3.9)%, P=0.145; 29.2+/-12.5 vs. 31.4+/-13.8, P=0.44]. At the concentration of 40 mug/ml, rituximab completely combined CD20 antigens on cell membrane. The obvious enhancive effect of rituximab on cell apoptosis appeared at 24 h after treatment. The killing rate of Raji cells was significantly higher in rituximab combined LAK group than in LAK group (P<0.05). While the combination of LAK cells and Herceptin (40 mug/ml) didn't make a significant increase as compared with Herceptin alone (P>0.05). There was no significant difference in killing rate of Jurket cells between rituximab combined LAK group and LAK group (P>0.05).

CONCLUSIONS

The down-regulation of CD16zeta chain expression widely exists in B-NHL patients, while high dose of IL-2 could enhance the expression of CD16zeta chain greatly in vitro. The combination of rituximab and LAK cells shows strong killing effect on Raji cells.