Significantly lower levels of anti-PC IgM are found in patients with mixed connective tissue disease (MCTD), and are negatively correlated with cardiovascular diseases not only in patients with MCTD, but also in patients with rheumatoid arthritis, systemic lupus erythematous (SLE), and undifferentiated connective tissue disease26,50. This evidence concerns the gene CD40LG and mixed connective tissue disease.