Studies on the susceptibility to NK-mediated lysis and the simultaneous expression of various surface molecules in anthracyclin-treated K562 cells and in four K562 cell clones

Establishment of cell lines stably expressing HNA-1a, -1b, and -2a antigen with low background reactivity in flow cytometric analysis

BACKGROUND

Antibodies to neutrophil antigens have been implicated in neonatal alloimmune neutropenia, autoimmune neutropenia, and transfusion-related acute lung injury. Most often, neutrophil-specific antibodies are directed toward human neutrophil antigen (HNA)-1 (Fcgamma receptor 3b) and HNA-2a (CD177) in these disorders.

STUDY DESIGN AND METHODS

To detect the alloantibodies in the serum samples, a panel of cell lines was established in which the HNA-1a, HNA-1b (polymorphisms of HNA-1), or HNA-2a gene was transduced with a retrovirus vector to confer stable transgene expression in K562 cells that exhibited low background reactivity to human serum samples obtained from healthy donors in flow cytometric analysis.

RESULTS

It was shown that several well-characterized human serum samples containing antibodies against HNA-1a, -1b, and -2a were unambiguously identified by the established panel cell lines and observed a lower background reactivity and longer shelf life of the K562 panel cell lines compared with isolated neutrophils, which have been used for the cell panel to identify antibodies against HNA in human serum samples.

CONCLUSION

These results indicate that the K562 panel cell lines provide a good panel for detecting HNA-reactive neutrophil antibodies in human serum samples.

PMA-treated K-562 leukemia cells mediate a TH2-specific expansion of CD4+ T cells in vitro

Highly enriched preparations of human CD3+CD4+ T-lymphocytes were stimulated with mitogen or OKT3 to determine the capacity of K-562 cells to function as accessory cells. Phorbol 12-myristate 13-acetate (PMA)-treated K-562 cells were induced to differentiate along the megakaryocytic lineage and could supplant monocyte-accessory cell function. Intracytoplasmic analysis of interleukin-4 (IL-4) and interferon-gamma (IFN-gamma) established that IL-4, and not IFN-gamma, was preferentially produced by the activated lymphocytes. This polarized stimulation is compatible with a type 2 or humoral immune response of purified T cells co-cultured with differentiated K-562 cells in vitro, and may have implications in immunoregulation due to disease progression.

Glycophorin A protects K562 cells from natural killer cell attack. Role of oligosaccharides

Glycophorin A is a protein with an abundant glycosylation (60% carbohydrate by weight), and studies have suggested that resistance of target cells to natural killing may be correlated with the level of glycophorin A expression. To assess the role of glycophorin A and of its carbohydrates in sensitivity to lysis by natural killer (NK) cells, the glycoprotein was inserted into the membrane of K562 target cells using electropulsation. Peripheral blood lymphocytes were used as effector cells. When glycophorin A was inserted into the membrane, the level of resistance to NK cell attack increased with the number of glycophorin A molecules electroinserted. The resistance to lysis was not due to a defect in target cell-effector cell binding. Electroassociation of glycophorin A did not cause a decrease in the expression of either "positive signals" for NK cells (such as CD71, CD15, and CD32 antigens) or cellular adhesion molecules (CD18, CD29, CD54, and CD58). Furthermore, electroinsertion of glycophorin A did not trigger any "negative signals," such as class I HLA antigen expression. Finally, it was shown that the sialic acid and O-linked oligosaccharides of glycophorin A did not play any role in its effect against NK cells. Conversely, the unique N-linked oligosaccharide was shown to be essential for resistance to occur.

LDL and acetyl-LDL inhibit the NK activity and are taken up by CD56+ lymphocytes

The effect of LDL and modified LDL (acetyl-LDL) was studied on human natural killer cell-mediated cytotoxicity against K562 cells. Incubation for 24 h of peripheral blood lymphocytes (PBL) with a high concentration (200 micrograms/ml) of LDL decreased the NK activity in some donors. After acetylation of the LDL protein (apoB), the modified-LDL systematically inhibited the NK function of PBL in a time- and dose-dependent manner. Inhibition mediated by acetyl-LDL (AcLDL) was significantly greater than that of LDL, indicating that the apoB modification can mediate the inhibition of the NK function. AcLDL also inhibited the NK activity of peripheral blood mononuclear cells, suggesting that, under our experimental conditions, monocytes are not efficient enough to protect NK cells against the adverse effects of modified-LDL. With a cytofluorimetric analysis, the internalization of acetyl-LDL by PBL was demonstrated and was only 3-4 times lower than LDL internalization in lymphocytes. It appeared to be time, temperature and dose dependent, saturable and different from the internalization mediated by the known scavenger receptors. Finally, CD14- CD3+ lymphocytes and CD14- CD56+ lymphocytes were able to internalize AcLDL in the same way. Our results suggest that in some in vivo circumstances, when the LDL concentration and/or the modified-LDL/LDL ratio increase in tissues, lipoproteins are internalized by NK cells and also can induce adverse effects on the NK function.