A Culture Collection of 50 Neisseria gonorrhoeae Isolates

A culture collection of 50 Neisseria gonorrhoeae isolates is available from the CDC & FDA Antibiotic Resistance Isolate Bank. Associated data include antibiotic susceptibility information for azithromycin, cefixime, cefpodoxime, ceftriaxone, tetracycline, ciprofloxacin, penicillin, and spectinomycin and linked whole-genome sequences.

Altered lymphocyte responses and cytokine production in mice deficient in the X-linked lymphoproliferative disease gene SH2D1A/DSHP/SAP

We have introduced a targeted mutation in SH2D1A/DSHP/SAP, the gene responsible for the human genetic disorder X-linked lymphoproliferative disease (XLP). SLAM-associated protein (SAP)-deficient mice had normal lymphocyte development, but on challenge with infectious agents, recapitulated features of XLP. Infection of SAP- mice with lymphocyte choriomeningitis virus (LCMV) or Toxoplasma gondii was associated with increased T cell activation and IFN-gamma production, as well as a reduction of Ig-secreting cells. Anti-CD3-stimulated splenocytes from uninfected SAP- mice produced increased IFN-gamma and decreased IL-4, findings supported by decreased serum IgE levels in vivo. The Th1 skewing of these animals suggests that cytokine misregulation may contribute to phenotypes associated with mutation of SH2D1A/SAP.

High- and low-potency ligands with similar affinities for the TCR: the importance of kinetics in TCR signaling

We have examined binding characteristics for a single TCR interacting with five of its different peptide/MHC ligands using surface plasmon resonance. We find that very small structural changes produce ligands with similar equilibrium binding affinities (K(D)) for the TCR, but vastly different potencies for T cell activation. Ligands with similar K(D)s induce similar amounts of total phospho-zeta but distinct patterns of zeta phosphorylation. Lower potency ligands induce only incomplete phosphorylation of TCR zeta and generally have faster off-rates. Therefore, the potency of TCR ligands is primarily determined by the half-life of the TCR-ligand complex and the consequent ability to induce complete phosphorylation of zeta.

Fidelity of T cell activation through multistep T cell receptor zeta phosphorylation

The T cell receptor (TCR) alphabeta heterodimer interacts with its ligands with high specificity, but surprisingly low affinity. The role of the zeta component of the murine TCR in contributing to the fidelity of antigen recognition was examined. With sequence-specific phosphotyrosine antibodies, it was found that zeta undergoes a series of ordered phosphorylation events upon TCR engagement. Completion of phosphorylation steps is dependent on the nature of the TCR ligand. Thus, the phosphorylation steps establish thresholds for T cell activation. This study documents the sophisticated molecular events that follow the engagement of a low-affinity receptor.