KLF1 encodes EKLF (erythroid Krüppel-like factor 1) which does not represent a blood group system. Variation in this gene is associated with In(Lu), a phenotype inherited in a dominant fashion. The In(Lu) phenotype is characterized by reduced expression of antigens of the Lutheran system and for P1, Inb, and AnWj antigens.

Description from GeneCards:
This gene encodes a hematopoietic-specific transcription factor that induces high-level expression of adult beta-globin and other erythroid genes. The zinc-finger protein binds to the DNA sequence CCACACCCT found in the beta hemoglobin promoter. Heterozygous loss-of-function mutations in this gene result in the dominant In(Lu) blood phenotype.