Shashikant R. Mehta

T-lymphocyte/monocyte interaction in response to phytohemagglutinin

Abstract Macrophage cooperation has been shown to be necessary for the thymus-derived lymphocyte to express many of its differentiated functions. The importance of macrophage-lymphocyte interaction has been extended to the study of nonimmunogenic mitogenesis. Utilizing human macrophages and T-cells prepared separately to greater than 98% purity, we have demonstrated a marked degree of dependence of the T-cell upon the macrophage for mitogenesis in response to phytohemagglutinin. The degree of dependence observed is greater than that seen with other human systems and on the order of that seen in the highly purified nonhuman systems. The nature of the physical interaction between the macrophage and the T-cell was visualized using conventional light microscopy and scanning electron microscopy. Lymphocytes were observed to form a semirosetting pattern around the macrophage very early following mitogenic stimulation. The lymphocytes were observed to proceed through early blastogenesis while in direct contact with the macrophage.

IDENTIFICATION OF HUMAN B CELL GROWTH FACTOR11This work was supported in part by NIH Grant CA21927, a grant from the King Faisal Foundation and an Institutional grant from the Interferon Research Fund.

ABSTRACT Isolation of a specific human B cell growth factor (BCGF) has been the focus of the present investigation. This factor has been separated from other cytokines present in lectin stimulated peripheral blood lymphocyte conditioned media by a combination of ion exchange chromatography and multiple gel filtration steps. The isolated soluble factor possesses a molecular weight of 12-13,000 daltons and is specific for stimulating S phase entry in a proportion of activated B lymphocytes.

Analysis of Guanylate Cyclase Activity by High-Pressure Liquid Chromatography

Abstract A method for the assay of guanylate cyclase which permits the correction of concurrent phosphatase and phosphodiesterase reactions has been developed using HPLC. The method, based on the conversion of tritium labelled guanosine triphosphate to tritium labelled cyclic guanosine monophosphate, uses [14C]-cGMP as the internal standard to account for the degradative and procedural-losses. Radiolabelled reaction products are isolated by high pressure liquid chromatography on a Partisil SAX column with a single step isocratic elution using 12.5 mM potassium phosphate buffer (pH 3.25). Since column recovery of the nucleotides is virtually quantitative and complete purification is achieved, the method possesses a high degree of accuracy and precision.