Paediatric nodal marginal zone B-cell lymphadenopathy of the neck: a Haemophilus influenzae-driven immune disorder?

Many hyperplasias and lymphomas of marginal zone B-cells are associated with infection. We identified six children and one adolescent with cervical lymphadenopathy showing prominent polyclonal nodal marginal zone hyperplasia (pNMZH) and four adolescents with monoclonal paediatric nodal marginal zone lymphoma (pNMZL). The clonality status was assessed using BIOMED-2-IG PCR analysis. Haemophilus influenzae was identified in all six cases of pNMZH that could be tested by direct culture (N = 3) or a very sensitive PCR for the H. influenzae gyrase gene in frozen materials (N = 5). H. influenzae was not detected in three pNMZLs and 28 non-specific reactive cervical lymph nodes of age-matched controls, except for a single control node that was obtained during oropharyngeal surgery for a cleft palate showing very low copy numbers of H. influenzae. pNMZH patients were younger than pNMZL patients (median age 12 versus 21 years). pNMZH showed a prominent nodular appearance with variable fibrosis without acute inflammation. Within the nodules, the expanded germinal centres and variably sized marginal zones were colonized by activated B-cells with weak expression of IgD and lack of CD10 and/or BCL6 expression. Some areas showed skewed light chain expression in plasma cells (4/5 cases lambda). In four cases tested, this was confirmed by flow cytometry for surface Ig (3/4 cases lambda). In contrast, pNMZL showed more extensive expansion of marginal zones by centrocytoid cells and often expression of BCL2 protein. Several H. influenzae strains are known to interact with the constant part of IgD on human B-cells, leading to their polyclonal proliferation and activation. We speculate that in vivo stimulation of IgD+ marginal zone B-cells by this bacterium may be implicated in this particular lymphadenopathy that should be distinguished from monoclonal pNMZL.

Role of zyxin in differential cell spreading and proliferation of melanoma cells and melanocytes.

Cell spreading, proliferation, and survival are modulated by focal adhesions linking extracellular matrix proteins, integrins, and the cytoskeleton. Zyxin is a focal-adhesion-associated phosphoprotein with one domain involved in the control of actin assembly and three protein-protein adapter domains implicated in the regulation of cell growth and differentiation. We characterized zyxin expression in normal human melanocytes and six melanoma cell lines in relation to cell spreading, growth, and differentiation using Western immunoblotting techniques, image analysis, flow cytometry, and confocal microscopy. We found that zyxin, focal adhesion kinase, and paxillin were significantly upregulated in melanoma cells compared to melanocytes. Zyxin expression directly related to cell spreading and proliferation and inversely related to differentiation, whereas focal adhesion kinase correlated only to cell spreading and paxillin did not significantly correlate with any of the parameters. Treatment of melanoma cells with 12-O-tetradecanoylphorbol-13-acetate downregulated zyxin expression, inhibited cell spreading and proliferation, and promoted differentiation. In contrast, 12-O-tetradecanoylphorbol-13-acetate, a mitogen for melanocytes, induced upregulation of zyxin expression in melanocytes. These findings are consistent with a role of zyxin in modulation of cell spreading, proliferation, and differentiation. Therapies directed at the downregulation of this focal adhesion phosphoprotein in melanoma cells implicate a new approach for controlling melanoma cell growth.