A human leukemic cell line (THP-1) cultured from the blood of a boy with acute monocytic leukemia is described. This cell line had Fc and C3b receptors, but no surface or cytoplasmic immunoglobulins. HLA haplotypes of THP-1 were HLA-A2, -A9, -B5, -DRW1 and -DRW2. The monocytic nature of the cell line was characterized by: (1) the presence of alpha-naphthyl butyrate esterase activities which could be inhibited by NaF; (2) lysozyme production; (3) the phagocytosis of latex particles and sensitized sheep erythrocytes; and (4) the ability to restore T-lymphocyte response to Con A. The cells did not possess Epstein-Barr virus-associated nuclear antigen. These results indicate that THP-1 is a leukemia cell line with distinct monocytic markers. During culture, THP-1 maintained these monocytic characteristics for over 14 months.

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We molecularly cloned a new Grb2 family member, named Grf40, containing the common SH3-SH2-SH3 motif. Expression of Grf40 is predominant in hematopoietic cells, particularly T cells. Grf40 binds to the SH2 domain–containing leukocyte protein of 76 kD (SLP-76) via its SH3 domain more tightly than Grb2. Incidentally, Grf40 binds to linker for activation of T cells (LAT) possibly via its SH2 domain. Overexpression of wild-type Grf40 in Jurkat cells induced a significant increase of SLP-76–dependent interleukin (IL)-2 promoter and nuclear factor of activated T cell (NF-AT) activation upon T cell receptor (TCR) stimulation, whereas the COOH-terminal SH3-deleted Grf40 mutant lacked any recognizable increase in IL-2 promoter activity. Furthermore, the SH2-deleted Grf40 mutant led to a marked inhibition of these regulatory activities, the effect of which is apparently stronger than that of the SH2-deleted Grb2 mutant. Our data suggest that Grf40 is an adaptor molecule involved in TCR-mediated signaling through a more efficient interaction than Grb2 with SLP-76 and LAT.

Human rotavirus was detected by electron microscopy in 11 of 30 infants and young children with intussusception (37% of subjects under study). Serologic complement fixation tests revealed evidence of infection with the rotavirus in 70% of the patients examined who eliminated the rotavirus in their stools. These results indicate that human rotavirus, in addition to adenovirus, may be an infectious agent causing intussusception in infants and young children.