VIRUS-SPECIFIC IGD IN ACUTE VIRAL-INFECTION OF MICE

In phylogenetically diverse species with the help of T lymphocytes or soluble factors, viral infections induce the Ag-specific B lymphocytes to proliferate and terminally differentiate into IgM, IgG, IgA, IgD, or IgE Ab-secreting cells. Based on previous studies searching for IgD , it was inferred that serum IgD in the mouse is nearly undetectable, although in other species, e.g., humans, IgD is a measurable component of serum Ig. More recently, new information has been obtained indicat ing that IgD is secreted in minute quantities during normal B cell dif ferentiation. We observed that IgD is secreted in significantly increa sed quantities in mice undergoing an acute infection with lymphocytic choriomeningitis virus or vesicular stomatitis virus compared with uni nfected animals. A substantial fraction of the observed IgD was found to be virus specific. Using a solid-phase immunoenzymatic technique, v irus-specific IgD Ah-forming cells were detected in the spleen; their numerical increase correlated with the level of secreted antiviral IgD . In addition, immunohistochemical staining revealed IgD(+) plasma cel ls that occurred with a similar kinetic profile as the virus-specific IgD Ab-forming cells. These findings provide direct evidence that synt hesis of IgD is a physiologic event in the mouse. Its precise function in the immune response to pathogens, however, remains to be determine d.