Effect of infections with swine fever virus on immune functions I. Response of lymphocytes from blood and lymphoid organs from infected and normal pigs to anti-immunoglobulin serum and protein A

Abstract

Pigs exposed to a low-virulent strain of swine fever virus (SFV) developed an inapparent infection. At times when a transient leucopenia occurred, the peripheral blood lymphocytes (PBL) were unresponsive to the mitogenic stimulus of anti-immunoglobulin serum (anti-Ig) and protein A. Pigs lethally infected with a virulent SFV showed leucopenia and unresponsiveness of PBL to anti-Ig and protein A from 2 days post infection until death. This suggests a defect in B lymphocyte function in pigs infected with SFV. The unresponsiveness to anti-Ig appeared not to be caused by a reduced ability of lymphocytes to redistribute their receptors into caps, the presence of suppressor cells or absence of surface immunoglobulin bearing lymphocytes in the peripheral blood. A direct action of the virus itself also seemed unlikely. Lymphocytes from spleen reacted as PBL. However, lymph node cells did not lose their capability to respond to anti-Ig. These data suggest that a change in the migration pattern of anti-Ig responsive lymphocytes could account for the observed unresponsiveness of PBL and spleen lymphocytes to anti-Ig.