CD4 and systemic lupus erythematosus: This massive citrullination of self-antigens (which also affects LL37) could be responsible for the higher expression of LL37-specific CD4 T cells with a Thf-like phenotype in SLE, which can be instrumental in driving the highly frequent autoantibody response to LL37 and modified LL37 in SLE patients (21, 22).