Figure 1: Serum total immunoglobulin levels (1a) and Ig-producing (1b) and Ig-secreting (1c) cells in old and young mice. 10 old (24 months of age) and 10 young (4 months of age) were bled and the 1: 5 × 105-diluted sera were assessed for the 19 levels of total Immunoglobulin, IgG, IgM and IgA with ELISA (1a). Compared to young mice, old mice exhibited significantly elevated levels of serum IgG (P<0.001), IgM (P<0.05) and IgA (P<0.0001). Four mice in each group were also bled for assessment of the frequencies and numbers of total Immunoglobulin IgG, IgM and IgA positive cells with Flow Cytometer (1b) and ELISPOT assay (1c). For Flow Cytometry analysis, 0.4 × 106 cells in each tube were stained with FITC- labeled rat anti-mouse Mab. For ELISPOT assay, 8 × 104 cells in 0.2 ml were equally distributed into two wells and the ELISPOT plates were scanned and analyzed by C.T.L Analyzers LLC (Cleveland, OH). Compared to young mice, old mice exhibited significantly increased frequencies and spot numbers of IgG (P<0.01-0.001), IgM (P<0.05-0.01) and IgA (P<0.05-0.01) positive cells. The data were presented in means ± SE. Compare the young and the old mice, *P<0.05-0.0001.