HLA-S and flatulence: Indeed, later studies revealed that allelic variations in human leukocyte antigen (HLA) class II haplotypes resulted in striking differences in severity and outcomes of invasive GAS infections via the differential presentations of GAS superantigens (SAgs) by class II HLAs to host T-cell receptor (TCR) Vβ elements; this finding further revealed a strong role for host factors in modulating GAS disease outcomes [11–14].