agglutinogen: any substance that acts as an antigen to cause agglutinin production
antigen: any substance (as a toxin or enzyme) that stimulates an immune response in the body (especially the production of antibodies)
closed universe: (cosmology) a universe that is spatially closed and in which there is sufficient matter to halt the expansion that began with the big bang; the visible matter is only 10 percent of the matter required for closure but there may be large amounts of dark matter