TY - JOUR
T1 - The Ia.2 epitope defines a subset of lipid raft-resident MHC class II molecules crucial to effective antigen presentation
AU - Busman-Sahay, Kathleen
AU - Sargent, Elizabeth
AU - Harton, Jonathan A.
AU - Drake, James R.
PY - 2011/6/15
Y1 - 2011/6/15
N2 - Previous work established that binding of the 11-5.2 anti-I-Ak mAb, which recognizes the Ia.2 epitope on I-Ak class II molecules, elicits MHC class II signaling, whereas binding of two other anti-I-A k mAbs that recognize the Ia.17 epitope fail to elicit signaling. Using a biochemical approach, we establish that the Ia.2 epitope recognized by the widely used 11-5.2 mAb defines a subset of cell surface I-Ak molecules predominantly found within membrane lipid rafts. Functional studies demonstrate that the Ia.2-bearing subset of I-Ak class II molecules is critically necessary for effective B cell-T cell interactions, especially at low Ag doses, a finding consistent with published studies on the role of raft-resident class II molecules in CD4 T cell activation. Interestingly, B cells expressing recombinant I-Ak class II molecules possessing a β-chain-tethered hen egg lysosome peptide lack the Ia.2 epitope and fail to partition into lipid rafts. Moreover, cells expressing Ia.2- tethered peptide-class II molecules are severely impaired in their ability to present both tethered peptide or peptide derived from exogenous Ag to CD4 T cells. These results establish the Ia.2 epitope as defining a lipid raft-resident MHC class II conformer vital to the initiation of MHC class II-restricted B cell-T cell interactions.
AB - Previous work established that binding of the 11-5.2 anti-I-Ak mAb, which recognizes the Ia.2 epitope on I-Ak class II molecules, elicits MHC class II signaling, whereas binding of two other anti-I-A k mAbs that recognize the Ia.17 epitope fail to elicit signaling. Using a biochemical approach, we establish that the Ia.2 epitope recognized by the widely used 11-5.2 mAb defines a subset of cell surface I-Ak molecules predominantly found within membrane lipid rafts. Functional studies demonstrate that the Ia.2-bearing subset of I-Ak class II molecules is critically necessary for effective B cell-T cell interactions, especially at low Ag doses, a finding consistent with published studies on the role of raft-resident class II molecules in CD4 T cell activation. Interestingly, B cells expressing recombinant I-Ak class II molecules possessing a β-chain-tethered hen egg lysosome peptide lack the Ia.2 epitope and fail to partition into lipid rafts. Moreover, cells expressing Ia.2- tethered peptide-class II molecules are severely impaired in their ability to present both tethered peptide or peptide derived from exogenous Ag to CD4 T cells. These results establish the Ia.2 epitope as defining a lipid raft-resident MHC class II conformer vital to the initiation of MHC class II-restricted B cell-T cell interactions.
UR - http://www.scopus.com/inward/record.url?scp=79959550940&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=79959550940&partnerID=8YFLogxK
U2 - 10.4049/jimmunol.1100336
DO - 10.4049/jimmunol.1100336
M3 - Article
C2 - 21543648
AN - SCOPUS:79959550940
SN - 0022-1767
VL - 186
SP - 6710
EP - 6717
JO - Journal of Immunology
JF - Journal of Immunology
IS - 12
ER -