In the chicken three types of T-cell receptors can be defined by monoc
lonal antibodies TCR1, TCR2 and TCR3, which recognize gammadelta T cel
ls, and Vbeta1- and Vbeta2-expressing alphabeta T cells, respectively.
In the present report we have analysed means of selectively depleting
the gammadelta T cells and the Vbeta1+ alphabeta T cells. Gammadelta
T cells, which represent up to 66% of all T cells in blood of a 6-mont
h-old chicken, can be effectively depleted by neonatal thymectomy (Tx)
to levels as low as 1%. Immunohistology demonstrates a similar deplet
ion in lymphoid organs while intestinal epithelium-associated gammadel
ta T cells are affected by Tx to a lesser extent. Vbeta1-bearing alpha
beta T cells, which comprise about 80% of the alphabeta T cells, were
depleted by embryonic and neonatal injection of the TCR2 antibody. In
the thymus such treatment depleted only the Vbeta1+ alphabeta T cells
with high density expression of T-cell receptor. Therefore, we thymect
omized TCR2-treated animals in order to prevent development of mature
Vbeta1+ alphabeta T cells from the low density immature thymocytes. Tr
eatment of chickens with a total of 22 mg of TCR2 antibody plus Tx red
uced Vbeta1+ alphabeta T cells from an average of 65% to 10% of all T
cells. In these TCR2 antibody-treated animals the Vbeta2-expressing al
phabeta T cells become the predominant type of T cell (average 85%).