Immunopotentiator, cell-mediated immunopotentiator, and t cell proliferation agent

An immunopotentiator including a collagen peptide that has an average molecular weight of 2,000-12,000. Immunity can be elevated, taking as an indicator an immunity score comprising the sum of the scores assigned to following seven parameters when a score of 1 (low immunity), 2 (medium immunity), or 3 (high immunity) on a scale of three established in advance in correspondence with levels of immunity is assigned to the measured values of each of the seven parameters: T cell count, CD8-positive CD28-positive T cell count, CD4-positive T cell/CD8-positive T cell ratio, naive T cell count, naive T cell/memory T cell ratio, B cell count, and NK cell count.