Rescue of W-associated mast cell defects in W/Wv bone marrow cells by ectopic expression of normal and mutant epidermal growth factor receptors

The normal human epidermal growth factor receptor (EGF-R) (HERc), a chimeric EGF-R/v-erbB (HERerbB) receptor, and the ligand-independent oncogenic EGF-R variant (v-erbB) were used to correct the mast cell defects in W/Wv bone marrow (BM) cells. In culture, all three receptor molecules transduced functional mitogenic signals in infected interleukin-3 (IL-3)-dependent bone marrow-derived mast cells (BMMCs) and enabled their differentiation into safranin-positive mast cells resembling connective tissue-type mast cells (CTMCs). Furthermore, expression of these receptors restored the capacity of W/Wv BMMCs to colonize the peritoneal cavity of mast cell-deficient W/Wv mice where they differentiated to safranin-positive cells with similar frequencies as wild-type BMMCs. These experiments show that expression of normal and mutant EGF-Rs in W/Wv BM cells is able to complement the function of the c-kit-encoded Steel factor receptor (SLF-R) in mast cell development. We conclude that signal transduction by normal and mutant EGF-Rs in murine hematopoietic cells apparently involves components also used by the SLF-R, which suggests that these receptors use overlapping pathways for signal transduction.     

Generation of human natural killer cells from immature progenitors does not require marrow stromal cells

Human natural killer (NK) cells comprise 10% to 15% of peripheral blood mononuclear cells and have an important role in immune responses against tumors, viral infections, and graft rejection. NK cells originate in bone marrow (BM), but their progenitors and lineage development have not been completely characterized. We studied the generation of NK cells from purified CD34+HLADR- and CD34+HLADR+ BM progenitors and the influence of various cytokines on their production. We show that CD3-CD56+ cytotoxic NK cells can develop from both progenitors populations when interleukin-2 (IL-2) is present in an in vitro suspension culture system containing IL-1 alpha and stem cell factor. Up to 83.8% and 98.6% CD3-CD56+ cells were detected in CD34+HLADR- and CD34+DR+ cultures, respectively, after 5 weeks of culture; significant numbers of NK cells were first detected after 2 weeks. Cytotoxic activity paralleled NK cell numbers; up to 70% specific lysis at an effector:target ratio of 10:1 was observed at 5 weeks. IL-7 also triggered development of CD3-CD56+ cells from these immature progenitors (up to 24% and 55% appeared in CD34+HLADR- and CD34+HLADR+ cultures, respectively). Our data suggest that BM stromas are not necessary for NK cell development and that IL-2 remains essential for this lineage development and differentiation.     

Large granular lymphocytes from patients with expanded LGL populations acquire cytotoxic functions and release lymphokines upon in vitro activation

The phenotypic and functional features of purified large granular lymphocytes (LGL) from ten patients with LGL population expansions and cytopenias are described. The predominant LGL phenotypes were T3+, T8+, Leu-11+/-; however, in two patients, LGL expressed a T3-, Leu-11+ phenotype. Variable combinations of other LGL markers (OKM1, Leu-7), and HLA-DR were detected in individual cases. In nine of ten cases, freshly isolated LGL did not exert cytolytic activity for K562 target cells, but purified LGL cultured in the presence of recombinant interleukin 2 (rIL2) acquired potent cytotoxic activity in all cases tested. LGL did not proliferate in response to phytohemagglutinin (PHA). However, LGL released variable amounts of IL2 and gamma- interferon (gamma-IFN) after PHA stimulation. In some cases, stimulation of fresh LGL with recombinant IL2 induced production of gamma-IFN. No correlation was found between the functional capabilities and the original phenotype of the expanded LGL populations.