C4A and systemic lupus erythematosus: Indeed, there are several findings of genetic or functional C4A null alleles in patients with SLE not carrying the HLA-DRB1*0301 genotype.2,33 The predominant HLA alleles appear to differ among global patient groups with various ethnic backgrounds, especially in nonwhite populations and in patients of non-European ancestry.30,34 In contrast, the C4A null allele appears not to be restricted to certain ethnicities in general.2,35