Xz. Zhou et al., PRESENTATION OF VIRAL-ANTIGENS RESTRICTED BY H-2K(B), D-B OR K-D IN PROTEASOME SUBUNIT LMP2-DEFICIENT AND LMP7-DEFICIENT CELLS, European Journal of Immunology, 24(8), 1994, pp. 1863-1868
In the class II region of the major histocompatibility complex (MHC),
four genes implicated in MHC class I-mediated antigen processing have
been described. Two genes (TAP 1 and TAP 2) code for multimembrane-spa
nning ATP-binding transporter proteins and two genes (LMP 2 and LMP 7)
code for subunits of the proteasome. While TAP 1 and TAP 2 have been
shown to transport antigenic peptides from the cytosol into the endopl
asmic reticulum, where the peptides associate with MHC class I molecul
es, the role of LMP 2/7 in antigen presentation is less clear. Using a
ntigen processing mutant T2 cells that lack TAP 1/2 and LMP 2/7 genes,
it was recently shown that expression of TAP 1/2 alone was sufficient
for processing and presentation of the influenza matrix protein M1 as
well as the minor histocompatibility antigen HA-2 by HLA-A2. To under
stand if presentation of a broader range of viral antigens occurs in t
he absence of LMP 2/7, we transfected T2 cells with TAP 1, TAP 2 and e
ither of the H-2K(b), D-b or K-d genes and tested their ability to pre
sent vesicular stomatitis vires and influenza virus antigens to virus-
specific cytotoxic T lymphocytes. We found that T2 cells, expressing T
AP 1/2 gene products, presented all tested viral antigens restricted t
hrough either the H-2K(b), D-b or K-d class I molecules. We conclude t
hat the proteasome subunits LMP 2/7 as well as other gene products in
the MHC class Il region, except from TAP 1/2, are not generally necess
ary for presentation of a broader panel of viral antigens to cytotoxic
T cells. However, the present results do not exclude that LMP 2/7 in
a more subtle way may, or in rare cases completely, affect processing
of antigen for presentation by MHC class I molecules.