Malaria and Schistosomiasis are the major endemic parasitic diseases in the world. The former is killing over one million children in Africa per year, and the latter suffers several millions in the endemic areas in Asia, Africa and South America. Collaborative studies were performed to identify some genetic factors contributing to the development of fatal forms of these infectious diseases. In Thailand, TNF-ﾎｱ 5\u27- flanking region showed biallelic polymorphic sites at -238, -308, -857, -863, -1031, and there were 7 alleles found in the patients from Myanmar. We found that the TNFP-D allele was significantly associated with cerebral malaria in the populations from Karen (Pc <0.0001, OR=124.86) and Burma (Pc <0.0001, OR = 34.50). In China, we have identified two major genes related to severity of liver fibrosis, one was HLA-class II and the other was IL-13 gene. The allele frequencies of HLA-DRB5*0101 and IL-13 promoter A/A homozygote were both increased in the fibrotic group although the two genes are located in the different chromosomes, Chromosome 6p and 5q. The person who had both genotypes showed much higher Odds Ratio (OR=24.5) compared with sum of either genotype positive persons (OR=5.1 for HLA-DRB5*0101, OR=3.7 for IL-13P A/A). The observation that the effect of the two susceptible markers were synergistic rather than additive, strongly suggested that the pathogenic Th2 response directly influence the prognosis of post-Schistosomal liver fibrosis
