High level expression of the plasma cell antigen PC.1 on the T-cell subset expanding in MRL/MpJ-lpr/lpr mice: detection with a xenogeneic monoclonal antibody and alloantisera

Cell Immunol. 1985 Dec;96(2):327-37. doi: 10.1016/0008-8749(85)90364-8.


MRL/MpJ-lpr/lpr (MRL-lpr/lpr) mice spontaneously develop a systemic lupus erythematosus-like syndrome associated with the expansion of a T-cell subset exerting helper activity for autoantibody production. Several studies have demonstrated that these T cells have unusual phenotypic characteristics including the expression of the B220 B-cell marker. To further characterize the antigenic profiles of these T cells, we have generated monoclonal antibodies (MAb) by immunizing rats with MRL-lpr/lpr T cells. Using flow cytofluorometry analysis, one of these MAb (4G6), described here, was found to react strongly with T cells of MRL-lpr/lpr mice but weakly with T cells of congenic mice lacking the lpr mutation (MRL/MpJ-+/+ mice). This MAb also stained brightly T cells from C3H/Hej-lpr/lpr mice and dimly those from normal C3H/Hej mice. However, it failed to react with T cells from C57Bl/6-lpr/lpr mice or normal C57Bl/6 (B6) mice. Analysis of 4G6 reactivity (weak vs negative) of T cells in a series of inbred strains demonstrated a correlation with the Pca-1a genotype known to result in expression of the PC.1 antigen on plasma cells. Immunoprecipitation studies revealed that the 4G6 antigen has a mean apparent molecular weight of 115,000, under reducing conditions, similar to that of PC.1. Moreover, high expression of 4G6 was found on plasmacytoma lines and B blasts but not on T blasts. Identity of the 4G6 antigen with PC.1 was confirmed by the finding that conventional anti-PC.1 alloantisera could block the cell surface binding of the 4G6 MAb. Therefore, T cells from MRL-lpr/lpr (and C3H-lpr/lpr) mice aberrantly carry high levels of a plasma cell antigen, detected by the 4G6 MAb, which substantiates further that these T cells represent a unique subset with some surface properties of the B-cell lineage.

MeSH terms

  • Animals
  • Antibodies, Monoclonal
  • Antigens, Surface / analysis*
  • Antigens, Surface / genetics
  • Autoimmune Diseases / immunology*
  • B-Lymphocytes / immunology
  • Lymph Nodes / immunology
  • Mice
  • Mice, Mutant Strains / genetics
  • Mice, Mutant Strains / immunology*
  • Molecular Weight
  • Plasma Cells / immunology*
  • T-Lymphocytes / immunology*
  • T-Lymphocytes, Regulatory / immunology*


  • Antibodies, Monoclonal
  • Antigens, Surface