Biosynthesis of membrane bound Ig and secretion of Ig by chicken lymphoid cells.

The metabolic turnover of membrane proteins of chicken lymphoid cells is studied, using a double isotope labeling technique (i.e., [14C]amino acid pulse and [3H]leucine chase). Compared with other membrane proteins, the metabolic turnover of membrane bound immunoglobulins (M-Ig) is very slow. There was no difference in the turnover between M-Ig and specific antigen binding receptor immunoglobulins. Immunoglobulins appear to be a stable constituent of the lumphocyte membrane. Cellular kinetic experiments show that the rate of biosynthesis of secreted immunoglobulins (S-Ig) is nearly ten times as much as that of M-Ig, suggesting that metabolic pathway leading to M-Ig are distinct from those leading to S-Ig. The difference in 3H/14C ratios between S-Ig and M-Ig reflects the rate of biosynthesis of these immunoglobulins by two types of bursa derived lymphoid cells.