Molecular basis of 9G4 B cell autoreactivity in human systemic lupus erythematosus.

9G4(+) IgG Abs expand in systemic lupus erythematosus (SLE) in a disease-specific fashion and react with different lupus Ags including B cell Ags and apoptotic cells. Their shared use of VH4-34 represents a unique system to understand the molecular basis of lupus autoreactivity. In this study, a large panel of recombinant 9G4(+) mAbs from single naive and memory cells was generated and tested against B cells, apoptotic cells, and other Ags.

Anergic responses characterize a large fraction of human autoreactive naive B cells expressing low levels of surface IgM.

B cell anergy represents an important mechanism of peripheral immunological tolerance for mature autoreactive B cells that escape central tolerance enforced by receptor editing and clonal deletion. Although well documented in mice, the extent of its participation in human B cell tolerance remains to be fully established. In this study, we characterize the functional behavior of strictly defined human naive B cells separated on the basis of their surface IgM (sIgM) expression levels.

Conformational heterogeneity of an equilibrium folding intermediate quantified and mapped by scanning mutagenesis.

It is challenging to experimentally define an energy landscape for protein folding that comprises multiple partially unfolded states. Experimental results are often ambiguous as to whether a non-native state is conformationally homogeneous. Here, we tested an approach combining systematic mutagenesis and a Brønsted-like analysis to reveal and quantify conformational heterogeneity of folding intermediate states.

Unfolding mechanics of multiple OspA substructures investigated with single molecule force spectroscopy.

We investigated mechanical unfolding of Borrelia burgdorferi outer surface protein A (OspA), a Lyme disease antigen containing a unique single-layer beta-sheet, with atomic force microscopy (AFM). We mechanically stretched a monomeric unit, rather than a tandem repeat, by pulling it from its N and C-terminal residues without using intervening polymer as a spacer. We detected two peaks in the force-extension profile before the final rupture of a fully extended polypeptide, which we interpreted as unfolding of multiple substructures in OspA.