Open AccessAntibody penetration of viable human cells. II. Anti‐RNP antibodies binding to RNP antigen expressed on cell surface, which may mediate the antibody internalization
Author(s) -
MA J.,
KING N.,
CHEN S.L.,
PENNY R.,
BREIT S. N.
Publication year - 1993
Publication title -
clinical & experimental immunology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.329
H-Index - 135
eISSN - 1365-2249
pISSN - 0009-9104
DOI - 10.1111/j.1365-2249.1993.tb08191.x
Subject(s) - snrnp , antibody , immunoelectron microscopy , ribonucleoprotein , antigen , microbiology and biotechnology , internalization , small nuclear ribonucleoprotein , biology , monoclonal antibody , polyclonal antibodies , immunofluorescence , epitope , immunoprecipitation , cell , immunology , biochemistry , rna , gene
SUMMARY As U1 small nuclear ribonucleoprotein (U1 snRNP 2 ) has a crucial role in pre‐mRNP splicing, the interaction of anti‐RNP antibody with snRNP within viable lymphocytes may profoundly influence cell functions. We have shown that antibody can penetrate viable human lymphocytes, and anti‐RNP antibodies enter more cells than other anti‐nuclear antibodies or control IgG. In order to study the in vitro interaction of anti‐RNP antibodies with viable cells. T lymphocytes were metabolically labelled with 35 S‐methionine, then incubated with the antibodies and washed. A set of 35 S‐labelled cell‐associated snRNP polypeptides A, B'/B, C and D were found to bind to both monospecific human polyclonal anti‐RNP IgG (human anti‐RNP IgG) and a mouse monoclonal anti‐RNP antibody (2.73), indicating that anti‐RNP antibodies interacted with RNP antigen inside or/and on the surface of viable cells. To investigate antibody binding to RNP antigen on the cell surface, the cell surface proteins were either iodinated with 125 I or the cells processed for immunoelectron microscopic studices after incubation with MoAb. At least seven 125 I‐labelled polypeptides on the cell surface were found to be immunoprecipitated by the anti‐RNP MoAb which have similar molecular weights to U snRNP polypeptidcs 70K, A, B, D, E, F, and G. The immunoelectron microscopic studies showed that the gold particles formed clustered patches on the cell membrane. Further studies suggested that RNP antigen bound to the cell surface, and the RNP binding structure was probably a heterodimer receptor. This study provides evidence to suggest that anti‐RNP antibody entry into viable cells may be mediated by interaction with RNP antigen expressed on the cell surface.