Early protein synthesis in activated human peripheral blood mononuclear cells.
Though B-cell division and Ig synthesis in response to pokeweed mitogen (PWM) require interaction with T-cells and monocytes, it is not clear which earlier events in B-cell activation share this requirement, and which are the result of direct interaction of mitogen with the B-cell. Having previously shown that the acceleration of lecithin synthesis in human B-cells at 16-20 hr requires both T-cells and monocytes, we now examine whether B-cells require similar interactions to increase their protein synthetic rate, another important activation event. At 21-24 hr of PWM stimulation, the stimulation index (SI) for incorporation of [35S]methionine into protein was 2.1 +/- 0.4 for unfractionated cells, 1.7 +/- 0.1 for B-cells, 2.5 +/- 0.1 for T-cells, and 3.4 +/- 0.5 for monocytes. Thus monocytes contributed substantially to early mitogen-induced protein synthesis by human peripheral blood mononuclear cells. When the monocyte/B-cell fraction (MB) and T-cell fraction (T) were mixed at various ratios in PWM-stimulated cultures, synergy was apparent at MB:T ratios of 1:1 and 1:2, indicating cell interactions augmented early mitogen-driven protein synthesis in at least one of these cell types. However, much or all of this synergy could be attributed to T-cells, whose protein synthetic response was augmented by B-cells and monocytes. In contrast, the early increase in B-cell protein synthesis appeared to be independent of cell interactions, since their SI of 1.7 was not influenced by varying the proportion of M- or T-cells over a 50-fold range. These contrasting results between two contemporary events fits the hypothesis that one (accelerated phospholipid synthesis) requires a first signal plus one or more cell interaction signals, whereas the other (accelerated protein synthesis) requires only the first signal.
D000328:Adult; D001402:B-Lymphocytes / Q000378:metabolism; D001798:Blood Proteins / Q000096:biosynthesis*; D002450:Cell Communication; D005260:Female; D006801:Humans; D007962:Leukocytes / Q000378:metabolism*; D008213:Lymphocyte Activation; D008297:Male; D008715:Methionine / Q000378:metabolism; D009000:Monocytes / Q000378:metabolism; D010835:Phytohemagglutinins / Q000494:pharmacology; D011043:Pokeweed Mitogens / Q000494:pharmacology; D013601:T-Lymphocytes / Q000378:metabolism
D001798:Blood Proteins; D010835:Phytohemagglutinins; D011043:Pokeweed Mitogens; D008715:Methionine