title: Elevated levels and functional capacity of soluble CD40 ligand in systemic lupus erythematosus sera.
abstract: OBJECTIVE
  To measure soluble CD40 ligand (sCD40L) in sera from patients with systemic lupus erythematosus (SLE) and to study the functional capacity of sCD40L in mediating B cell activation.
  
  
  METHODS
  A 2-site enzyme-linked immunosorbent assay (ELISA) was used to measure sCD40L in the sera of 66 SLE patients, 30 disease control patients, and 23 healthy subjects. Induction of B cell activation antigen expression was used to assess the functional capacity of sCD40L in SLE sera.
  
  
  RESULTS
  The mean concentration of sCD40L was statistically significantly higher (P < 0.0001) in SLE patients than in disease controls or healthy subjects, and segregation of SLE patients by severe, moderate, or mild extent of disease showed a relationship between disease severity and sCD40L concentration. Western blot analysis demonstrated the presence of the 18-kd band of sCD40L in SLE sera, and the results of a 1-site ELISA protocol suggested that some of the product in SLE sera was present in dimer or trimer form. Functional studies showed that 10 ng/ml of recombinant CD40L, a level present in some SLE sera, induced increased expression of CD95 on B cells. Several SLE sera also induced CD95 or CD86 on Ramos B cells, a result that was inhibited by anti-CD40L monoclonal antibodies.
  
  
  CONCLUSIONS
  The soluble form of CD40L is present in the sera of most patients with SLE and may have the capacity to mediate B cell activation. Aberrant expression of CD40L might be predicted to result in activation of bystander B cells, including those that have encountered self antigens, and to contribute to autoantibody secretion.
mesh_terms: D000954:Antigens, Surface / Q000096:biosynthesis; D001172:Arthritis, Rheumatoid / Q000097:blood; D001402:B-Lymphocytes / Q000276:immunology; D019013:CD40 Antigens / Q000097:blood / Q000737:chemistry; D023201:CD40 Ligand; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D008024:Ligands; D008180:Lupus Erythematosus, Systemic / Q000097:blood*; D008562:Membrane Glycoproteins / Q000097:blood* / Q000494:pharmacology; D008970:Molecular Weight; D011994:Recombinant Proteins / Q000494:pharmacology; D012995:Solubility