TNF and graft versus host disease: On the other hand, some inflammatory mediators including histamine, prostaglandin, corticosteroids and cytokines, especially tumor necrosis factor alpha (TNF-α) which are pivotal in the pathophysiology of GVHD are encoded by HLA-related genes.31 Bouma et al demonstrated that the HLA-DR1-related TNF haplotype presents a low-secretor phenotype and produces lower levels of TNF-α in comparison with other HLA alleles.