+ Site Statistics
+ Search Articles
+ PDF Full Text Service
How our service works
Request PDF Full Text
+ Follow Us
Follow on Facebook
Follow on Twitter
Follow on LinkedIn
+ Subscribe to Site Feeds
Most Shared
PDF Full Text
+ Translate
+ Recently Requested

Characterization of epitopes of human secretory component on free secretory component, secretory IgA, and membrane-associated secretory component



Characterization of epitopes of human secretory component on free secretory component, secretory IgA, and membrane-associated secretory component



Journal of Immunology 133(4): 2116-2125



We have compared the epitopes present in various forms of human secretory component by using a panel of hybridoma-derived antibodies elicited by immunizing mice with free secretory component (FSC) or secretory IgA (sIgA). Enzyme-linked immunosorbent binding assays (ELISA) were used to assess antibody binding to FSC- and SC-containing antigens, including sIgA isolated from milk, reduced and alkylated sIgA, and sIgA assembled in vitro by incubating dimeric IgA with FSC. Immunofluorescence assays were also used to assess binding to a human epithelial tumor cell line (HT29) that expresses secretory component as an integral protein of the plasma membrane. The results can be summarized as follows. 1) Most antibodies from fusions in which sIgA was the immunizing antigen bound preferentially to sIgA. 2) Most antibodies from fusions in which FSC was the immunizing antigen bound preferentially to FSC. 3) Antibodies that bound preferentially to sIgA invariably bound sIgA assembled in vitro; antibodies that bound preferentially to FSC invariably did not. 4) Antibodies that bound readily to both sIgA and FSC were rare in all fusions. 5) The monoclonal antibodies defined at least six classes of epitopes on SC, including epitopes that were a) FSC specific and reduction sensitive, b) FSC specific and reduction insensitive, c) sIgA specific and reduction-sensitive, d) sIgA specific and reduction insensitive, e) shared by FSC and sIgA and reduction-sensitive, and f) shared by FSC and sIgA and reduction-insensitive. 6) Antibodies that mediated intense immunofluorescent staining of secretory component on HT29 cell membranes were rare and constituted a distinct subset of those which recognized epitopes shared by FSC, reduced and alkylated sIgA, and some preparations of native sIgA. Results of these antibody-binding studies indicate that most SC epitopes are not shared by FSC and sIgA. Most SC-related epitopes on sIgA appear to be generated by the physical interaction of SC with dimeric IgA, whereas most epitopes on FSC are masked or altered by this interaction. Finally, epitopes that are shared by membrane SC and FSC and/or sIgA represent a minor and immunochemically distinct subset of epitopes on SC. The high proportion of unique epitopes on the different physical forms of SC suggest that the epitopes of this molecule are highly sensitive to its molecular environment. The monoclonal reagents described here will be useful in studying the structure and function of SC; quantitating FSC, sIgA, and membrane SC; purifying various molecular forms of SC by immunoaffinity chromatography; and localizing SC in human tissues and cultured cells by immunocytochemical techniques.

Please choose payment method:






(PDF emailed within 1 workday: $29.90)

Accession: 042513709

Download citation: RISBibTeXText

PMID: 6206152


Related references

Studies on human secretory IgA. II. Comparative studies on a fragment of secretory component derived from secretory IgA and fragments obtained by enzymatic digestion of free secretory component. Immunochemistry 10(2): 73-80, 1973

Human secretory component. II. Physicochemical characterization of free secretory component purified from colostrum. Scandinavian Journal of Immunology 3(6): 707-716, 1974

The membrane receptor for polymeric immunoglobulin is structurally related to secretory component. Isolation and characterization of membrane secretory component from rabbit liver and mammary gland. Journal of Biological Chemistry 256(23): 12490-5, 1981

Differences between the in vitro combinations of secretory component and immuno globulin polymers by enumeration of secretory component epitopes. Immunology Letters 7(4): 195-202, 1984

Human secretory component. IV. Aggregation and fragmentation of free secretory component. Immunochemistry 12(11): 877-881, 1975

Human secretory component. I. Purification of free secretory component from colostrum. Scandinavian Journal of Immunology 3(5): 579-588, 1974

Cleavage of membrane secretory component to soluble secretory component occurs on the cell surface of rat hepatocyte monolayers. Journal of Cell Biology 104(6): 1725-1734, 1987

Rat liver membrane secretory component is larger than free secretory component in bile: evidence for proteolytic conversion of membrane form to free form. Journal of Cellular Biochemistry 24(4): 307-317, 1984

Examination of human keratinocytes for immunoreactive secretory component and for secretory component messenger rna. Journal of Investigative Dermatology 94(4): 508, 1990

Isolation and characterization of secretory IgA (sIgA) and free secretory component (FSC) from rat bile. Molecular Immunology 17(12): 1525-1537, 1980

Purification of free secretory component and secretory immuno globulin a from human milk. Federation Proceedingspart 1: 968, 1973

Esterase activity associated with secretory IgA and free secretory component preparations from human milk. Biochimica et Biophysica Acta 317(2): 517-523, 1973

Secretory IgA, secretory component and pathogen specific antibodies in the middle ear effusion during an attack of acute and secretory otitis media. Auris Nasus Larynx 12(Suppl. 1): S180-S182, 1985

Human secretory component. II. Easy detection of abnormal amounts of combined secretory component in human sera. Journal of Immunological Methods 28(3-4): 331-340, 1979

Localization of free and bound secretory component in human intestinal epithelial cells. A model for the assembly of secretory IgA. Journal of Experimental Medicine 139(3): 629-642, 1974