Page 384 - Veterinary Immunology, 10th Edition

VetBooks.ir Species Differences

Horses

Horse lymphocytes express two species-specific proteins. EqWC1 is
found on 70% of equine T cells, 30% of B cells, and 50% of
granulocytes and may be a homolog of CD90. EqWC2 is found on

granulocytes and most T cells.

Bovine

Cattle lymphocytes express the species-specific cell surface
molecules BoWC1 through BoWC15. (BoWC3 is now known to be

CD21; BoWC6 is CD205, a C-type lectin expressed on dendritic
cells; and BoWC10 is CD26).
In adult cattle, about 10% to 15% of circulating T cells have γ/δ
TCRs, whereas the remainder have α/β TCRs. In young calves the

proportion of γ/δ T cells may rise to 40%. However, this proportion
fluctuates in response to management and stress. The majority of
bovine γ/δ T cells also express WC1. Indeed, these cells can be
activated either through their TCR or through WC1. In response

they produce TNF-α, IL-1, IL-12, and IFN-γ. This mixture suggests
that they contribute to both inflammation and a Th1 bias in the
bovine immune response and thus link the innate and adaptive
immune systems.

CD4 is expressed on 20% to 30% of blood lymphocytes in adult
ruminants. Double-negative T cells constitute 15% to 30% of the
blood T cells in young ruminants, but this may reach 80% in
+
newborn calves. Most of these double-negative cells are γ/δ and
+
+
+
WC1 . Thus the major circulating T cells in ruminants (γ/δ , WC1 ,
−
−
CD4 , CD8 ) are different from the predominant T cells in the
−
−
+
+
humans and mice (α/β , WC1 , CD4 , CD8 ).
Sheep
Sheep T cells express OvWC1 (also called T19). The isoform of this
molecule expressed on α/β T cells differs from that on γ/δ T cells. In
newborn lambs, γ/δ T cells account for 60% of blood T cells, but this

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