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Anti-Immunoglobulin Stimulation of Murine Lymphocytes

IV. Re-Expression and Fate of Cell Surface Receptors During Stimulation¹

From the Division of Clinical Immunology, Department of Medicine, University of Colorado Medical School, Denver, Colorado 80262

Abstract

Anti-immunoglobulin (anti-Ig) stimulation of spieen cells from aged mice (7 to 9 months old) results in both blast cell transformation and increased incorporation of ³H-TdR. Younger animals rarely respond to anti-Ig. Using the above parameters to measure cell activation we investigated 1) the time requirements for anti-Ig-lymphocyte interaction which are necessary to induce stimulation, 2) the identity of the responding cells, and 3) the fate of surface receptors on the stimulated cells.

When spleen cells were cultured with anti-Ig for various periods of time, it was found that the anti-Ig antibodies had to remain in culture for at least 48 hr of the 3-day culture period to induce maximum stimulation. Removing anti-Ig from culture at 24 or 4 hr resulted in a significantly lower response or an inhibition of proliferation. The cells responding to anti-Ig were B cells; 85 to 90% of anti-Ig-induced blast cells, cultured to allow re-expression of surface markers, were positive for surface Ig which was IgM.

The prolonged requirement for anti-Ig in culture indicated that surface Ig must be continuously re-expressed by the responding cells. However, free surface Ig was not detected on the cells during continuous culture with anti-Ig. Rather, the cells were found to have relatively large amounts of rabbit antibody bound to their surface. Similar cultures stimulated with F(ab')₂ fragments or cultures of spleen cells from young animals stimulated with intact anti-Ig did not have surface-bound rabbit antibody. The rabbit antibody is most likely in the form of antigen-antibody complexes, i.e., surface Ig-anti-Ig, bound to Fc receptors on the stimulated cells. These complexes are apparently produced by the continuous re-expression and redistribution of surface Ig by anti-Ig, a process that is required for anti-Ig stimulation of B cells.

Footnotes

¹ This work was supported in part by National Institutes of Health Grant AG-00464 and the Colorado Multiple Sclerosis Society.

² Fellow of the Colorado Multiple Sclerosis Society. Present address: Department of Microbiology, Harvard Medical School, Boston, Massachusetts 02115.

³ Postdoctoral trainee of the United States Public Health Service.

⁴ Recipient of National Institutes of Health Research Career Development Award 1-KO4-AI-00125.

⁵ Reprint requests should be addressed to John W. Moorhead, Ph.D., Division of Clinical Immunology, University of Colorado Medical School, Denver, Colo. 80262.