Bruton's tyrosine kinase (
) deficiency preferentially eliminates autoreactive B cells while sparing normal humoral responses, but has not been studied in mucosal immunity. Commensal microbes and ...intact BTK signaling have been independently shown to be essential for arthritis development in K/BxN mice. Here, we examine how BTK-mediated signaling interfaces with the gut microbiome.
-deficient K/BxN mice were found to have small Peyer's Patches with reduced germinal center and IgA class-switched B cells. IgA-switched plasma cells in small intestines were reduced, especially in villi of
-deficient mice. IgH CDR3 sequencing showed similar V gene diversity and somatic hypermutation frequency despite
deficiency but showed reduced CDR3 amino acid polarity, suggesting potential qualitative differences in the gut plasma cell repertoire. Small intestinal IgA was low and IgA coating of commensal bacteria was reduced. IgA-seq showed a shift in small intestinal microbes that are normally IgA-coated into the uncoated fraction in
-deficient mice. Overall, this study shows that BTK supports normal intestinal IgA development in response to commensals. This manuscript was previously published as a preprint at: https://www.biorxiv.org/content/10.1101/2021.03.10.434762v2.
Hybrid self-assembled monolayers (SAMs) containing well-defined strata of different polarity enable insight into how fundamental interactions lead to higher order structure and may provide useful ...analogies for self-assembled multilayers, new hybrid materials, and functional biological interfaces. We report amide-containing alkanethiol SAMs with internal polar sublayers that are two amide groups thick and nonpolar overlayers comprising either dodecyl or hexadecyl chains. The assemblies have been characterized by X-ray photoelectron spectroscopy (XPS), contact angle goniometry, and external reflective infrared spectroscopy (FTIR-ERS). XPS demonstrates the SAMs are of monolayer thickness, chemisorbed to the gold substrate, and anisotropically oriented. Contact angle data show the methyl surface for n = 16 is highly ordered, but the surface for n = 12 is less well ordered. FTIR-ERS reveals that the alkyl chains for n = 16 are close packed, but that those for n = 12 are disordered. FTIR-ERS also shows that, although the two-amide sublayers are compositionally identical, they are well ordered and assume polyglycine-II-like conformations for n = 16, but they are poorly ordered for n = 12. Comparison of these two SAMs to each other in the context of previously reported one- and three-amide SAMs leads to two conclusions. (1) The threshold n for alkyl chain length ordering in two-amide SAMs is 12 ≤ n ≤ 16. Thus, in SAMs with internal amide sublayers both one and two amide groups thick, the threshold number of methylenes required to form ordered alkyl regions is significantly increased compared to alkanethiol SAMs, demonstrating destructive interference of the amide region with the hydrocarbon ordering process. (2) In two-amide SAMs the formation of a well-ordered amide region depends on the ordering of an overlying hydrocarbon region. This behavior differs with that previously demonstrated for one- and three-amide SAMs, in which the amide groups assume characteristic conformations regardless of hydrocarbon region thickness and order. For two-amide SAMs, the apparent dependence of amide ordering on complementary ordering in the alkyl region provides evidence of an energetic interplay between the two sublayers, manifested as a “reverse ordering” effect. The previously unobserved elastic−elastic character of the buried interface in two-amide SAMs is contrasted with the rigid−elastic interface found in the one-amide SAMs.
PDF
