Practice question

Enzyme-linked immunospot assay visualizes individual secretory cells through local capture of released cytokines. Plates are coated with high-affinity anti-cytokine capture antibody. Peripheral blood mononuclear cells are incubated briefly, during which activated T cells secrete interferon-gamma or interleukin. Secreted cytokine is immediately captured around each producing cell, forming microscopic immune complex footprint. Subsequent biotinylated detection antibody and enzymatic development create colored spots, each spot representing one cytokine-producing cell. Unlike RIA, Western blot or agglutination that measure bulk analyte, ELISpot provides frequency analysis crucial for vaccine response and cellular immunity studies.