Dose-dependent effect of histamine on antibody generation in vivo

To delineate immunomodulatory role of histamine on antibody generation profile in rabbit in the present dose-dependent histamine study. The cohort comprised of three groups (III, IV and V), containing six rabbits each, and received subcutaneous histamine 50 μ g/kg × bis in die (b.i.d.), 100 μg/kg × b.i.d. and 200 μg/kg × b.i.d., respectively for 10 days (starting from the 1st day). They were subsequently immunized on the 3rd day with intravenous injection of sheep blood cell (SRBC) (1×109 cells/mL). Group II (positive control) (n=6) received vehicle (sterile distilled water) and immunized at day 3 similarly while group I (negative control) (n=6) remained non-immunized and received only vehicle. All experimentations were performed in triplicate. Blood samples were collected on pre-immunization (pre-I) (day 0), as well as on days 7-, 14-, 21-, 28- and 58- post-immunization (post-I). Immunological parameters [total immunoglobulins (Igs), IgM and IgG] were analyzed by enzyme linked immunosorbent assay (ELISA) technique. Histamine could influence a detectable antibody response to SRBC as early as day 7-post-I, which lasted until day 58- post-I. The results were found statistically significant (P < 0.05). Our results provide evidence that histamine has a short-term effect on antibody generation (until its presence in the body), and the antibody generation titer in vivo were affected by the concentration of histamine.