PMID: 6403541Apr 25, 1983Paper

The requirement of light chain for the surface deposition of the heavy chain of immunoglobulin M.

The Journal of Biological Chemistry
P E Mains, C H Sibley

Abstract

The murine tumor line 70Z/3 resembles a pre-B lymphocyte in containing the heavy chain of IgM (mu) as a cytoplasmic protein in the apparent absence of light chain (L). However, these cells can be induced by lipopolysaccharide to differentiate into a B lymphocyte-like state, containing mu2L2 tetramers as membrane-bound molecules. This is a accompanied by an increase in mu synthesis, the acquisition of complex carbohydrate by mu, and the induction of L chain. We wished to determine which of these events is critical for membrane deposition of mu. We found that uninduced 70Z/3 cells, as well as lipopolysaccharide-uninducible variants, contained a low, constitutive level of membrane bound mu, all of which was found as mu2L2. Dextran sulfate, another inducing agent, apparently caused a redistribution of this pre-existing surface mu without altering the pattern of mu synthesis or processing. One lipopolysaccharide-uninducible variant showed a small subset of surface mu-positive cells, and the proportion of these cells increased with a prolonged induction period. The increase in mu synthesis was nearly normal, but mu did not acquire complex carbohydrate. However, the delayed appearance of surface mu-positive cells was paralleled by a d...Continue Reading

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