Evidence for defects in accessory and T cell subsets in mice expressing the xid defect

Mice expressing the X-linked recessive CBA/N genetic defect xid lack a subpopulation of B cells which appears late in normal B cell ontogeny and is characterized by expression of the cell surface antigens Lyb3, Lyb5, and Lyb7. In adult mice with the xid defect, responses to Type 2 antigens such as TNP-ficoll are entirely absent and responses to Type 1 antigens such as TNP-LPS are somewhat reduced. Primary in vitro responses to the T dependent antigen sheep red blood cells (SRBC) are defective but secondary responses are normal. These and other findings have led to the hypothesis that one effect of the xid defect is the inability of a subset of B cells to respond to nonspecific signals from T cells or accessory cells. The cellular basis of the xid defect is not well understood. The simplest explanation is that it reflects a primary lesion in the development of a subpopulation of B cells responsible for the types of immune responses described above. An alternative notion is that the xid defect is expressed primarily in a non-B cell population (e.g., T cells or accessory cells) which are necessary for the development and/or function of this B cell subset. A direct approach to this problem depends on the availability of homogeneous populations of B cells, T cells, or accessory cells. Recently we have described a cloned dendritic cell, Den-1, which is a potent stimulator of some B and T cell responses.(ABSTRACT TRUNCATED AT 250 WORDS)