Calcium pyrophosphate deposition disease (CPPD) is a common and clinically heterogeneous form of arthritis caused by the deposition of calcium pyrophosphate (CPP) crystals in articular tissues. The diagnosis of CPPD is supported by the presence of radiographic chondrocalcinosis; yet, conventional radiography detects only about 40 % of clinically important CPPD. Here, we critically review the recent literature on imaging in CPPD. New studies inform our use of conventional radiographic screening methodologies for CPPD and provide additional evidence for the utility of diagnostic ultrasound. Recent work also highlights the polyarticular nature of CPPD, its association with tissue damage, and the high prevalence of tendon involvement. While dual energy CT and diffraction-enhanced synchrotron imaging remain research tools, they present potential avenues for improved visualization of CPP deposits. Advances in imaging in CPPD will increase diagnostic accuracy and eventually result in better management of this common form of arthritis.

Pathogenic anti-DNA antibodies expressed in systemic lupus erythematosis bind DNA mainly through electrostatic interactions between the positively charged Arg residues of the antibody complementarity determining region (CDR) and the negatively charged phosphate groups of DNA. The importance of Arg in CDR3 for DNA binding has been shown in mice with transgenes coding for anti-DNA V H regions; there is also a close correlation between arginines in CDR3 of antibodies and DNA binding. Codons for Arg can readily be formed by V(D)J rearrangement; thereby, antibodies that bind DNA are part of the preimmune repertoire. Anti-DNAs in healthy mice are regulated by receptor editing, a mechanism that replaces κ light (L) chains compatible with DNA binding with κ L chains that harbor aspartic residues. This negatively charged amino acid is thought to neutralize Arg sites in the V H . Editing by replacement is allowed at the κ locus, because the rearranged VJ is nested between unrearranged Vs and Js. However, neither λ nor heavy (H) chain loci are organized so as to allow such second rearrangements. In this study, we analyze regulation of anti-DNA H chains in mice that lack the κ locus, κ-/κ-mice. These mice show that the endogenous preimmune repertoire does indeed include a high frequency of antibodies with Arg in their CDR3s (putative anti-DNAs) and they are associated mainly with the editor L chain λx. The editing mechanisms in the case of λ-expressing B cells include L chain allelic inclusion and V H replacement.autoimmunity | tolerance A nti-DNA antibodies bind DNA mainly through electrostatic interactions between the positively charged Arg (R) residues of the antibody complementarity determining regions (CDRs) and the negatively charged DNA phosphodiester backbone (1). Arg enrichment has been demonstrated in the protein sequences of anti-DNA antibody heavy (H) chains (2, 3). In addition, reverse mutagenesis of an H chain Arg to a germline amino acid weakened DNA binding, whereas forward mutagenesis with additional Arg residues enhanced DNA binding (1). The predominant occurrence of Arg residues in the V H -encoded CDRs of anti-DNA antibodies indicates a dominant role for V H in DNA binding, and the DNA specificity of these H chains persists when paired with a wide variety of light (L) chains (4-6). There are exceptional L chains (4 Vκ L chains of 95 functional Vκ genes and 1 Vλ L chain of 4 functional Vλ L chains) of the mouse that modify or veto the DNA-binding quality of 7,8). These editor L chains are characterized by a high content of aspartate, a negatively charged amino acid that efficiently neutralizes the positively charged Arg residues of anti-DNA H chains (4). B cells that express an anti-DNA V H with a noneditor L chain can undergo further L chain rearrangement. If the original L chain is replaced by an editor L chain, the B cell will be tolerized (4, 7). Similarly, MHC class I-reactive B cells (found in 3-83μ transgenic mice) that encounter autoantigen in the bone marrow continue rearrangement and change rece...