Evaluation of Immune System Traits in Reciprocal Angus-Brahman F1 Crosses
Abstract
The influence of sex and reciprocal cross type on cell-mediated immune responses following in vitro exposure of Bovine Viral Diarrhea Virus (BVDV) were evaluated in Brahman-Angus F1 cattle for across two trials. Lymphocyte populations were stimulated with BVDV Type 1 (BVDV1) and Type 2 (BVDV2) genotypes. In Trial 1 (n = 48) T cells from Brahman-sired animals consistently ranked approximately 20% higher for BVDV positivity (BVDV+) than those from Angus-sired animals pre-MLV vaccination. Post-MLV vaccination, T cells from Angus-sired animals were ranked 20% higher (P < 0.05) for CD2+, CD4+, and CD8+ cells. Post-MLV steers consistently had 30-35% higher (P < 0.05) frequencies of T cells BVDV+ following viral exposure; steers had higher frequencies (P < 0.05) of CD4+ and CD335+ cells expressing IFN-, and ranked higher for CD2+ and CD8+ cells when compared to heifers in both crosses. There were no significant correlations involving BVDV antibody titers and T cell responses. When stimulated with BVDV2, positive correlations of 0.33 to 0.39 (P < 0.05) were observed between cell frequencies for BVDV presence and IFN- expression within cell type, but these correlations were not significant when stimulated with BVDV1, except for CD335+ (r = 0.41, P = 0.003). In Trial 2 (n = 19), Angus-sired animals had an 85% higher (P = 0.032) proportion of CD335+ cells, while having 38% lower (P < 0.001) proportion of CD4+ cells regarding total lymphocyte numbers. Angus-sired cattle were 26% higher for cell frequency of Indoleamine 2,3-dioxygenase-1 (IDO) expression in CD335+ cells (P = 0.001) and 58% higher (P = 0.018) for total lymphocytes. Bulls (n = 4) consistently ranked higher than steers (n = 15) for cell frequency of IDO expression for all cells but were 73% higher (P = 0.012) for total lymphocytes. Bulls also ranked higher for cell frequency of programmed cell death-1 (PD-1) expression by 58.2% in CD4+ (P = 0.025). Bulls had a tendency to rank higher in frequency of PD-1 and IDO expression
across all cell types. Differences in cell mediated responses involving reciprocal cross types and sex observed in this project may relate to widely reported reciprocal cross differences in birth weight in Bos indicus-Bos taurus crossbred cattle and warrant additional study.
Citation
Chapman, MacKenzie Gail (2022). Evaluation of Immune System Traits in Reciprocal Angus-Brahman F1 Crosses. Master's thesis, Texas A&M University. Available electronically from https : / /hdl .handle .net /1969 .1 /198780.