Peripheral blood lymphocyte subsets in fleece rot-resistant and -susceptible sheep.
OBJECTIVE
To compare haematological values and lymphocyte phenotypes in the peripheral blood of fleece rot-resistant and -susceptible sheep.


METHODS
Experiments were conducted on 2- and 3-year-old Merino rams, flock 1 (17 rams) and flock 2 (32 rams), respectively. Within each flock, individual rams were classified as fleece rot-resistant or -susceptible, based on established criteria. Total and differential white cell counts, and indirect fluorescent antibody tests specific for B cells and T cells were performed on all sheep. The concentration of various subsets of circulating lymphocytes was then determined in each sheep.


RESULTS
There were no significant differences between fleece rot-resistant and -susceptible sheep from either flock in the mean total or differential white cell counts. However, fleece rot-resistant rams in flock 1 did have a significantly higher concentration of circulating SBU-T1+ cells than fleece rot-susceptible rams from the same flock. No such difference was noted in the rams from flock 2. While all rams in flock 1 were free of clinical fleece rot, 24 rams in flock 2 (comprising all 17 fleece rot-susceptible and 7 of 15 fleece rot-resistant animals) had clinical signs of the disease. Fleece rot-free rams in this flock (irrespective of their classification as fleece rot-resistant or -susceptible) had significantly higher concentrations of circulating SBU-T1+ cells compared with fleece rot-affected animals. They also had significantly higher concentrations of circulating B cells, and total lymphocytes.


CONCLUSIONS
An examination of peripheral blood lymphocyte subsets in fleece rot-resistant and -susceptible sheep revealed a possible association between resistance to fleece rot and the concentration of circulating SBU-T1+ cells.
McColl
K A
KA
Elizabeth McArthur Agricultural Institute, NSW Department of Agriculture, Menangle.
Gogolewski
R P
RP
Chin
J C
JC
D000818:Animals; D000917:Antibody Formation / Q000502:physiology; D001402:B-Lymphocytes / Q000166:cytology / Q000276:immunology; D004198:Disease Susceptibility / Q000662:veterinary; D019084:Fluorescent Antibody Technique, Indirect / Q000662:veterinary; D007958:Leukocyte Count / Q000662:veterinary; D016131:Lymphocyte Subsets / Q000166:cytology* / Q000276:immunology; D008297:Male; D010641:Phenotype; D011552:Pseudomonas Infections / Q000097:blood / Q000276:immunology / Q000662:veterinary*; D012756:Sheep; D012757:Sheep Diseases / Q000097:blood / Q000235:genetics / Q000276:immunology*; D017192:Skin Diseases, Bacterial / Q000097:blood / Q000276:immunology / Q000662:veterinary*; D013601:T-Lymphocytes / Q000166:cytology / Q000276:immunology; D014935:Wool