Cellular and Antibody Mediated Immune Responses Are Influenced By Sex and Pregnancy Status in Mature Brahman Cattle

Measures of immune responsiveness are under evaluation as criteria to select breeding bulls and cows. The objective of this experiment was to determine whether cell-mediated immune response (CMIR) and antibody-mediated immune response (AMIR) varied according to sex and pregnancy status in mature Brahman cattle. We hypothesized that sex and pregnancy status would influence CMIR and AMIR. Status groups included 84 sexually mature, non-pregnant Brahman cows, 163 pregnant Brahman cows, and 25 fertile Brahman bulls in the Texas A&M AgriLife Research herd. For CMIR determination cattle were administered a 25x10³ protein nitrogen units (PNU)/mL subcutaneous (neck) sensitization dose of Candida albicans (CA; Greer Labs, Lenoir, NC) with 750 µg of Quil-A (InvivoGen, San Diego, California) adjuvant in 2.5 mL buffer on d0. On d14 after sensitization, tail skin fold thickness (SFT) was measured using a Harpenden caliper prior to intradermal injection of 5x10³ PNU/mL of CA in 0.5 mL in the skin fold. On d15 the injection site SFT was measured. Response was determined by the difference of SFT from d15 (post-injection) and d14 (pre-injection). For AMIR determination cattle were administered Salmonella Newport Extract vaccine (2 mL subcutaneous; Zoetis, Florham Park, NJ) on d0. Blood samples were collected by jugular venipuncture on d0 and d15. Serum samples were stored at -20C until analyzed for vaccine specific IgG by a double sandwich, enzyme linked immunosorbent assay. Data were analyzed using mixed model procedures of JMP (Cary, NC). Table 1 contains the mean CMIR and AMIR for bulls and non-pregnant and pregnant cows. Mean CMIR was greater (P<0.05) in pregnant cows and bulls than non-pregnant cows. Fertile bulls and pregnant cows did not differ in CMIR (P>0.05). With AMIR, fertile bulls and non-pregnant cows did not differ from each other; however the AMIR of these 2 groups exceeded (P<0.05) that of pregnant cows. A statistical relationship between CMIR and AMIR was not detected as correlation coefficients were near zero. The hypotheses that sex and pregnancy status affect CMIR and AMIR in cattle were accepted. Therefore, physiological status and sex should be considered when evaluating either cellular or antibody mediated immune response in mature Brahman cattle.

Table1- Comparison of cell-mediated immune response (CMIR) and antibody-mediated immune response (AMIR) among status groups in Brahman cattle (LSM±SE).

Sex Class	CMIR	AMIR
Non-pregnant cows (n=84)	5.763±0.591b	1.074±0.07a
Pregnant cows (n=163)	10.778±0.424a	0.521±0.05b
Fertile bulls (n=25)	12.136±1.083a	1.371±0.127a

^a,bMeans bearing different superscripts within columns differ at P<0.05.