Follicular dendritic cells help establish follicle identity and promote B cell retention in germinal centers.

Follicular dendritic cells (FDCs) retain and display opsonized antigens in primary follicles and germinal centers (GCs). However, their roles beyond antigen presentation have been incompletely defined. In this study, we tested the impact of selective FDC ablation on short-term follicle and GC function. Within 2 d of FDC ablation, primary follicles lost their homogeneity and became disorganized bands of cells around T zones. These B cell areas retained CXCL13-expressing stromal cells but often exhibited inappropriate ER-TR7 and CCL21 expression. Ablation of GC FDCs led to the disappearance of GCs. When B cell death was prevented using a Bcl2 transgene, FDC ablation led to splenic GC B cell dispersal. Mesenteric lymph node GCs were more resistant but became dispersed when sphingosine-1-phosphate receptor-2 was also removed. These experiments indicate that FDCs help maintain primary follicles as a B cell exclusive niche and define a critical role for FDCs in cell retention within GCs.

The sphingosine 1-phosphate receptor S1P2 maintains the homeostasis of germinal center B cells and promotes niche confinement.

Mice deficient in sphingosine 1-phosphate receptor type 2 (S1P(2)) develop diffuse large B cell lymphoma. However, the role of S1P(2) in normal germinal center (GC) physiology is unknown. Here we show that S1P(2)-deficient GC B cells outgrew their wild-type counterparts in chronically established GCs. We found that antagonism of the kinase Akt mediated by S1P(2) and its downstream mediators Gα(12), Gα(13) and p115RhoGEF regulated cell viability and was required for growth control in chronically proliferating GCs. Moreover, S1P(2) inhibited GC B cell responses to follicular chemoattractants and helped confine cells to the GC. In addition, S1P(2) overexpression promoted the centering of activated B cells in the follicle. We suggest that by inhibiting Akt activation and migration, S1P(2) helps restrict GC B cell survival and localization to an S1P-low niche at the follicle center.

Hydroxychloroquine and lichen planopilaris: efficacy and introduction of Lichen Planopilaris Activity Index scoring system.

BACKGROUND: Lichen planopilaris (LPP) and its variant frontal fibrosing alopecia (FFA) are primary lymphocytic cicatricial alopecias for which there is no evidence-based therapy. OBJECTIVE: We assessed the efficacy of hydroxychloroquine in active LPP and FFA using the LPP Activity Index (LPPAI), a numeric score that allows quantification of the symptoms and signs of the condition for statistical comparison. In addition, we determined with the LPPAI if any improvement (reduction) in the numeric score pretreatment and posttreatment reached statistical significance. METHODS: This was a retrospective, single-center chart review of 40 adult patients with LPP, FFA, or both who were treated with hydroxychloroquine for up to 12 months from 2004 to 2007 at the University of California, San Francisco Hair Center. Symptoms, signs, activity, and spreading were scored at each visit in the standardized cicatricial alopecia flow chart. A numeric score was assigned to these markers of disease activity and a numeric score was calculated at each visit. RESULTS: There was significant reduction (P < .001) in the LPPAI at both 6 and 12 months. After 6 months, 69% had improved (reduced) symptoms and signs. At 12 months, 83% had improvement (reduction) in symptoms and signs. LIMITATIONS: Retrospective analysis and uncontrolled study are limitations. CONCLUSIONS: Hydroxychloroquine is effective in decreasing symptoms and signs in LPP and FFA as shown by significant reduction in the LPPAI in 69% and 83% of patients after 6 and 12 months of treatment, respectively.

Efficacy and safety of mycophenolate mofetil for lichen planopilaris.

BACKGROUND: Lichen planopilaris (LPP) is a chronic inflammatory disorder that causes permanent scalp hair loss and significant patient discomfort. OBJECTIVES: We sought to determine the efficacy and safety of mycophenolate mofetil (MMF) for treatment of LPP in patients who had failed prior topical, intralesional, or oral anti-inflammatory medications such as hydroxychloroquine or cyclosporine. METHODS: We conducted a retrospective chart review of 16 adult patients with LPP treated with at least 6 months of MMF in an open-label, single-center study from 2003 to 2007. Subjective and objective end points were quantified using the LPP Activity Index (LPPAI) and scores before and after treatment were assessed using a paired t test. Adverse events were monitored. RESULTS: Patients who completed treatment with MMF had significantly decreased signs and symptoms of active LPP despite having failed multiple prior therapies (P < .005). Five of 12 patients were complete responders (LPPAI score decreased>85%), 5 of 12 patients were partial responders (LPPAI score decreased 25%-85%), and two of 12 patients were treatment failures (LPPAI score decreased<25%). Four patients withdrew from the trial because of adverse events. LIMITATIONS: Retrospective analysis and small sample size were limitations. CONCLUSIONS: MMF was effective at reducing the signs and symptoms of active LPP in 83% of patients (10 of 12) who had failed multiple prior treatments after at least 6 months of treatment.

Fatal diffuse alveolar damage in two lung transplant patients treated with cetuximab.

Organ transplant recipients are at increased risk for aggressive cutaneous squamous cell carcinomas (cSCC) that recur and metastasize despite treatment with surgery, radiation, or both. Therapies targeting the epidermal growth factor receptor (EGFR) are being explored as treatments for metastatic cSCC. We describe our experience with two single-lung transplant patients who developed metastatic cSCC; failed surgical resection, radiation or chemoradiation therapy; and were ultimately treated with an EGFR inhibitor, cetuximab. Both patients died shortly after initiation of cetuximab due to diffuse alveolar damage, suggesting that EGFR inhibitors should be used with extreme caution in lung transplant recipients.

A peptide that antagonizes TCR-mediated reactions with both syngeneic and allogeneic agonists: functional and structural aspects.

We identify and consider some characteristics of a peptide antagonist for the Ag-specific receptor on 2C cells (the 2C TCR). The peptide, GNYSFYAL (called GNY), binds to H-2K(b), and a very high-resolution crystal structure of the GNY-K(b) complex at 1.35 A is described. Although the GNY peptide does not bind to L(d), the potency of GNY-K(b) as an antagonist is evident from its ability to specifically inhibit 2C TCR-mediated reactions to an allogenic agonist complex (QLSPFPFDL-L(d)), as well as to a syngeneic agonist complex (SIYRYYGL-K(b)). The crystal structure and the activities of alanine-substituted peptide variants point to the properties of the peptide P4 side chain and the conformation of the Tyr-P6 side chain as the structural determinants of GNYSFYAL antagonist activity.