The present study was carried out at the Department of Poultry and Fish Production, Faculty of Agriculture at Menoufia University, Shibin El-kom. The aim of the present study was to determine the concentration of immunoglobulin G (IgG) and investigate its relation to some blood constituents in chickens. Pullets were divided into three groups, control, high and low groups, based on IgG concentrations in blood serum.
The most important results can be summarized in the following points:-
1.   The high immune response group (HR) had the highest IgG concentration (13.68± 0.339 mg/dl) as compared to both of control (10.11±0.362 mg/dl) and the low IgG (7.20±0.339 mg/dl) groups. The statistical differences among groups were highly significant (p≤0.01).
2.   There was a positive relationship between the immune response to SRBC antigen and hemoglobin concentration, hematocrit percentage, red blood cell counts, white blood cell counts, total plasma protein concentration, albumin and globulin concentration.
3.   In general, the present results concluded that a complex relationship between immunoglobulin G and immunological and hematological traits of the chickens. The injection of SRBC as a natural antigen induced superior values of antibody response which resulted in good performance of some blood constituents in chickens.