OBJECTIVETo establish a novel flow cytometry-based assay for measuring the expression of lysosomal-associated membrane protein 1 (LAMP-1, CD107α) on the cell surface of natural killer (NK) cells and cytotoxic T lymphocyte (CTL) and evaluate the screening value of this assay for cytotoxic defects-related diseases such as familial hemophagocytic lymphopro-liferative (FHL) syndrome.

METHODThree suspected Chediak-Higashi Syndrome (CHS) patients, three suspected FHL patients and 10 healthy children were enrolled in the study from October 2010 to June 2011. Their PBMCs were separated and activated overnight with IL-2. After the granule release of NK cells activated by phytohemagglutinin (PHA) and CD8+T cells by anti-CD3, the CD107α expression were analyzed by flow cytometry. The peripheral blood DNA and RNA of the patients were extracted to analyze the pathogenic genes via DNA-PCR/RT-PCR and direct sequencing.

RESULTThe CD107α expression on CTL in the ten healthy children significantly increased after activation by anti-CD3 [(0.18 ± 0.07)% vs. (4.47 ± 2.36)%, P < 0.05] and NK cells after activation by PHA [(0.27 ± 0.07)% vs. (5.80 ± 2.83)%, P < 0.05]. The frequency of CD107α-expression NK cells in three suspected CHS after activation was significantly elevated when compared with the healthy control [0.5%, 0.6% vs. (5.80 ± 2.83)%] except patient 2. After the anti-CD3 activation, the frequency of CD107α expression on CTL cells also showed no significant difference [0.3%, 0.9%, 0.2% vs. (4.47 ± 2.36)%] in three patients. All of their mean fluorescence intensity (MFI) showed the same trend. Patient 1 and 3 were identified to have LYST mutations (Patient 1: c.5411-5414 del TTTC, L1741fsX1758 and c.7975 C > T, R2596X; Patient 3: c.4863G > A, R1563H and c.5392-5393delAA, E1739fsX1756). There was no mutation identified in the LYST gene for patient 2. CD107α expression of NK cells and CTL in the suspected FHL patients and in mirror of these findings, no underlying gene variation of PRF, MUNC13-4 and STX11 were identified.

CONCLUSIONWe developed a method to quantitatively assess cytotoxicity of the NK cells and CTL by measuring the expression of CD107α on the cell membrane, which appeared to be an effective and rapid screening test for cytotoxic defects-related diseases such as FHL and other HLH secondary to primary immunodeficiency.