Aj. Okragly et al., BOVINE GAMMA-DELTA T-CELL PROLIFERATION IS ASSOCIATED WITH SELF-DERIVED MOLECULES CONSTITUTIVELY EXPRESSED IN-VIVO ON MONONUCLEAR PHAGOCYTES, Immunology, 87(1), 1996, pp. 71-79
Bovine gamma/delta T cells have been shown previously to proliferate w
hen cocultured with gamma-irradiated bovine monocytes in the 'autologo
us mixed leucocyte reaction' (AMLR). It was suggested that the respons
e may be to culture-derived or culture-induced antigenic epitopes. Dat
a presented here indicate that the gamma/delta T-cell stimulatory acti
vity is attributable to a self-derived cell-surface molecule of mononu
clear phagocytes that is constitutively expressed in vivo. The ability
to induce an AMLR did not require in vitro culture or stress associat
ed with in vitro isolation of cells or increased temperature since it
could be induced by monocytes fixed by paraformaldehyde during blood c
ollection from normal animals. Furthermore, stimulation by monocytes d
id not depend upon secreted molecules since fixed monocytes that had b
een incubated overnight at 37 degrees to allow secretion of preformed
molecules, or subjected to hypotonic shock in H2O for 10 min before ad
dition to the cultures, induced an AMLR as did plasma membranes prepar
ed from ex vivo monocytes. In contrast, enzymatic treatment of monocyt
es to digest surface molecules followed by fixation destroyed their ab
ility to stimulate an AMLR. The ability of monocytes to stimulate prol
iferation of gamma/delta T cells was distinguishable from their abilit
y to stimulate alpha/beta T cells, since the former was destroyed by g
lutaraldehyde fixation whereas stimulation of alpha/beta T cells by ma
jor histocompatibility complex (MHC)-presented antigenic epitopes is n
ot. Moreover, induction of proliferation of bovine gamma/delta T cells
was not MHC-restricted. Finally, bovine alveolar macrophages, sheep m
onocytes and transformed bovine monocytes stimulated proliferation of
bovine gamma/delta T cells whereas none of the following did so: human
monocytes, murine macrophages, bovine myeloid cells other than mononu
clear phagocytes, other nucleated cells found in bovine blood includin
g activated MHC class II-bearing B cells, and a variety of species of
bacteria. Thus, the stimulatory epitope is unique to and conserved amo
ng mononuclear phagocytes of ruminants. Demonstration of stimulation o
f bovine gamma delta T cells by self-derived molecules is consistent w
ith reports for murine gamma/delta T cells.