This study will investigate the effects of a dose-dependent exposure of thimerosal on cell proliferation. First, thimerosal will be exposed to immortalized lymphocyte cell lines from autistic and non-autistic individuals as part of the AGRE collection, as well as human B cells. Both cell number and apoptosis will be examined before and after treatment. These results will be used to examine changes in cell proliferation (cell number) on an individual level with symptoms of autism including severity of disease, recovery, intestinal symptoms, immune function, and vaccination history. Finally, the RNA will be extracted from the lymphocytes and a whole genome array will be conducted on those lymphocytes with the largest change in cell proliferation, as well as five unaffected siblings. The investigators anticipate that cell proliferation will be a more sensitive measure than apoptosis in detecting differences in susceptibility to mercury exposure in lymphocytes from autistic and non-autistic individuals. The results of this research will facilitate advances in the understanding of the cause of autism. What this means for people with autism: This study will use the existing AGRE resource to examine if more sensitive endpoints are possible to determine the effects of environmental toxicants on cellular function. By doing so, it will facilitate knowledge into the understanding of the causes of autism.