KRT18 and systemic lupus erythematosus: In rheumatic diseases, two HML2 Env proteins (associated with HERV-K10 and the above mentioned HERV-K18 proviruses) were investigated in systemic lupus erythematosus (SLE) and Sjögren syndrome to assess their ability to stimulate humoral immunity, showing albeit no significant increase of specific Abs as compared to healthy controls (Herve et al., 2002).