Fc receptor-like 4 and 5 define human atypical memory B cells.

Atypical memory B cells accumulate in chronic infections and autoimmune conditions, and commonly express FCRL4 and FCRL5, respective IgA and IgG receptors. We characterized memory cells from tonsils on the basis of both FCRL4 and FCRL5 expression, defining three subsets with distinct surface proteins and gene expression. Atypical FCRL4+FCRL5+ memory cells had the most discrete surface protein expression and were enriched in cell adhesion pathways, consistent with functioning as tissue-resident cells. Atypical FCRL4-FCRL5+ memory cells expressed transcription factors and immunoglobulin genes that suggest poised differentiation into plasma cells. Accordingly, the FCRL4-FCRL5+ memory subset was enriched in pathways responding to endoplasmic reticulum stress and IFN-γ. We reconstructed ongoing B-cell responses as lineage trees, providing crucial in vivo developmental context. Each memory subset typically maintained its lineage, denoting mechanisms enforcing their phenotypes. Classical FCRL4-FCRL5- memory cells were infrequently detected in lineage trees, suggesting the majority were in a quiescent state. FCRL4-FCRL5+ cells were the most represented memory subset in lineage trees, indicating robust participation in ongoing responses. Together, these differences suggest FCRL4 and FCRL5 are unlikely to be passive markers but rather active drivers of human memory B-cell development and function.

A phenomenological approach to psychoprosthetics.

The phenomenology of human embodiment can advance the practitioner's understanding of the lived human body and in particular, what it means to incorporate a prosthetic device into one's body. In order for a prosthesis to be incorporated into the lived body of the patient, the prosthesis must arguably be integrated into the body schema. This article uses the phenomenology of Maurice Merleau-Ponty and others to identify three of the necessary conditions of embodiment that determine the body schema: corporeal understanding, transparency and sensorimotor feedback. It then examines the structure of each of these conditions of embodiment and how they impact the lived body's incorporation of prostheses and other artifacts. [Box: see text].

A novel function of RNAs arising from the long terminal repeat of human endogenous retrovirus 9 in cell cycle arrest.

The human genome contains approximately 50 copies of the replication-defective human endogenous retrovirus 9 (ERV-9) and thousands of copies of its solitary long term repeat (sLTR) element. While some sLTRs are located upstream of critical genes and have enhancer activity, other sLTRs are located within introns and may be transcribed as RNAs. We found that intronic RNAs arising from U3 sLTRs of ERV-9 were expressed as both sense (S) and antisense (AS) transcripts in all human cells tested but that expression levels differed in malignant versus nonmalignant cells. In nonmalignant cells, AS was expressed at higher levels than S and at higher levels than in malignant cells; in malignant cells, AS was expressed at amounts equivalent to those of S RNA. Critically, U3 AS RNA was found to physically bind to key transcription factors for cellular proliferation, including NF-Y, p53, and sp1, indicating that such RNA transcripts may function as decoy targets or traps for NF-Y and thus inhibit the growth of human cancer cells. Indeed, short U3 oligodeoxynucleotides (ODNs) based on these RNA sequences ably inhibited proliferation of cancer cell lines driven by cyclins B1/B2, the gene targets of NF-Y.

Complex mechanisms for inhibition of immunoglobulin gene expression in a germinal center B cell line.

CD40 ligation and IL-4 stimulation are critical Th2 cell-derived signals that act on germinal center B cells to stimulate immunoglobulin isotype switching. In addition to this well-known effect, these same Th2 signals have also been reported to inhibit ongoing immunoglobulin synthesis in germinal center B cells. To study the mechanism of this inhibition, we have investigated which immunoglobulin gene regulatory regions might be affected by IL-4 and CD40 Ligand (CD40L). CL-01 cells, a human B cell line of germinal center phenotype, were transiently transfected with luciferase reporter constructs containing various light and heavy chain enhancers and promoters; the cells were then incubated with or without CD40L and IL-4 and then assayed for luciferase expression. We find that the intronic enhancer of the kappa light chain (but not the heavy chain) is upregulated by CD40 ligation, but that VH and Vkappa promoters and the 3' enhancers of both the kappa and heavy chain loci are inhibited by CD40 ligation and the Th2 cytokines IL-4 and IL-10. The inhibitory response of the 3'alpha enhancer can be observed with a 130 bp core fragment of the enhancer, and remains unaffected by mutations in several motifs known or suspected to contribute to enhancer function. The ultimate effects of cytokines and CD40 ligation on immunoglobulin gene transcription therefore represent a complex integration of positive and negative stimuli acting on enhancers and promoters.

Detection of isotype switch rearrangement in bulk culture by PCR.

When a B lymphocyte changes from synthesizing IgM to synthesizing IgG, IgA, or IgE, this isotype switch is generally accompanied by a unique DNA rearrangement. The protocols in this unit describe two polymerase chain reaction (PCR)-based strategies for detecting switch rearrangements in bulk culture. The first involves direct PCR across the switch junctions, providing the opportunity for characterizing the recombination products by nucleotide sequence analysis; however, because of characteristics inherent to the PCR methodology this strategy cannot easily be used as a quantitative assay for recombination. A support protocol details the preparation of the 5' Su PCR probe for this protocol. The second basic protocol describes a method known as digestion-circularization PCR (DCPCR) that is more amenable to quantitation but yields no information on structure of the recombination products. Both techniques should be capable of detecting reciprocal deletion circles as well as functional recombination products remaining on the expressed chromosome.