The ontogeny of blood cells, complement, and immunoglobulins in 3- to 12-week-old 15I5-B congenic white Leghorn chickens.

Six partially developed line 15I5-B congenic White Leghorn chicken strains were used to investigate age and B haplotype effects on hematocrit, total and differential leukocyte counts, hemolytic complement, immunoglobulins, and body weights. The .C-12 line had the lowest hematocrit values throughout the study. The .15I-5 line always had the highest mean hematocrit value and differed from the .C-12 and .P-13 lines at 3, 8, and 12 weeks, as well as lines .N-15 and .6-2 at 12 weeks. Ontogenically, the total leukocyte, hemolytic complement, immunoglobulins, and body weight values increased after 3 weeks in all lines. Lymphocytes were the predominant leukocyte after 3 weeks in all lines studied. At 12 weeks, the .C-12 line had the highest total leukocytes, heterophils, lymphocytes, and monocytes among the lines studied. The .6-2 line had a significantly higher hemolytic complement level than the .P-13 or the .C-12 line at all 3 ages, and at 12 weeks it also differed from the .7-2 line. The lines were found to be comparable for immunoglobulin classes M and G. In this study the line 15I5-B congenic lines differ for the traits of hematocrit and hemolytic complement level, and the results suggest the difference may be determined by genes in the B complex.