PubMed · 4539705
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K Henry. 1972. The lymphoreticular system: morphological organization.. https://doi.org/10.1136/jcp.25.11.1003-b
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With the widespread use of yeast two-hybrid systems, many heterodimeric forms of S100 proteins have been found, although their biological significance is unknown. In the present study, S100A1 was found to interact with another S100 protein, S100P, by using the yeast two-hybrid system. The binding parameters of the interaction were obtained using an optical biosensor and show that S100P has a slightly higher affinity for S100A1 (K(d)=10-20 nM) when compared with that for self-association (K(d)=40-120 nM). The physical interaction of S100A1 and S100P was also demonstrated in living mammalian cells using a fluorescence resonance energy transfer technique. Preincubation of recombinant S100P with S100A1, before the biosensor assay, reduced by up to 50% the binding of S100P to a recombinant C-terminal fragment of non-muscle myosin A, one of its target molecules. Site-specific mutations of S100P and S100A1, combined with homology modelling of an S100P/S100A1 heterodimer using known S100P and S100A1 structures, allowed the hydrophobic interactions at the dimeric interface of the heterodimer to be defined and provide an explanation for the heterodimerization of S100P and S100A1 at the molecular level. These results have revealed the similarities and the differences between the S100P homodimer and the S100A1/S100P heterodimer.
Gene expression profiling was used to compare the gene expression patterns of human germinal center (GC) T helper (Th) cells with other CD4+ T-cell subsets (naive, central, and effector memory T cells). GC-Th cells, specifically localized in germinal centers to help B cells, are distantly related to central and effector memory T cells in global gene expression profiles. GC-Th cells displayed substantial differences in mRNA for adhesion molecules, chemoattractant receptors, and cytokines compared with other populations. Distinct expression of transcriptional factors by GC-Th cells is consistent with the hypothesis that they may be different from other T cells in cell lineage. Interestingly, CXCL13, a critical chemokine for B-cell entry to lymphoid follicles, is one of the most highly up-regulated genes in GC-Th cells. GC-Th cells (but not other T cells) produce and secrete large amounts of functional CXCL13 upon T-cell receptor activation, a process that is dependent on costimulation, requires translation and transcription, and is dramatically enhanced by activation in the presence of GC-B cells. This study revealed for the first time the unique gene expression program of GC-Th cells.
In the June 11 issue of Cell, Kraus et al. (2004) show, through conditional mutagenesis, that mature B cells have a drastically reduced life span in the absence of normal B cell antigen receptor (BCR) surface expression or tonic signal transduction. These studies support a role for signal transduction downstream of the BCR, rather than continued surface expression per se for the maintenance and survival of mature B cells in the periphery. Further, these studies exclude transient INF(gamma)-induced activation as a prerequisite to apoptosis in receptor-less cells.