M. Sandor et al., AN ALTERNATIVE FC-GAMMA-RECEPTOR LIGAND - POTENTIAL ROLE IN T-CELL DEVELOPMENT, Proceedings of the National Academy of Sciences of the United Statesof America, 91(26), 1994, pp. 12857-12861
Fetal pre-T cells express low-affinity receptors for IgG (Fc gamma R)
at a developmental stage prior to the rearrangement and expression of
immunoglobulin genes. The present studies investigated the possible fu
nctional significance of Fc gamma R on fetal pre-T cells. Between 13 a
nd 17 days of fetal development a subpopulation of T-cell receptor(-),
Thy-1(+) thymocytes expresses Fc gamma R. The same cells contain mRNA
for several forms of Fc gamma R (Fc gamma RII beta 1, beta 2, and Fc
gamma RIII). Concurrently, a Pgp-1(-), Thy-1(-), surface-immunoglobuli
n(-) fetal thymic cell binds recombinant soluble Fc gamma R. In princi
ple this cell can interact with the pre-T cells through this counter-r
eceptor. To test this possibility anti-Fc gamma RII/III antibody (2.4G
2) was injected into pregnant mice and then into their offspring for 6
wk postpartum. The injected antibody induced a slight increase in the
proportion of CD4 or CD8 single-positive, alpha/beta T cells in the t
hymus. However, in fetal thymic cultures in the presence of 2.4G2 or t
he recombinant soluble Fc gamma R there was an accelerated differentia
tion of thymocytes to single-positive, CD3-bright, heat-stable antigen
-dull, alpha/beta T cells. These experiments show that Fc gamma Rs are
present on pre-T cells during early fetal thymic development, and tha
t a non-IgG Ligand of the Fc gamma R is expressed concurrently on Thy(
-) fetal thymocytes. Furthermore, the presumed interaction of Fc gamma
R and the alternative ligand(s) influences T-cell development. IgG bi
nding could be an adapted function of Fc gamma Rs, and, as shown for m
any members of the Ig super family, these receptors may have originall
y served as cell-cell recognition/interaction molecules required for h
ematopoietic development.