H2BC21 and systemic lupus erythematosus: Additionally, the KEGG pathways analysis revealed the enrichment of pathways involved in immune responses and the pathways “systemic lupus erythematosus”, “alcoholism”, and “neutrophil extracellular trap formation” (Figure 3E), which consist of histone genes (H2A, H2B, H2C, and H4C histone families).