Hyperexpressed hairy leukemic cell Ii might bind to the antigen-presenting site of class II MHC molecules.

The p35 protein which is hyperexpressed on hairy leukemic cells was determined to be Ii, the electrophoretically invariant glycoprotein that is associated with class II major histocompatibility complex (Ia) antigens from the time of their synthesis. The principal function of class II MHC antigens is to present to T cell receptors those digested foreign antigenic peptides that probably fold as amphipathic alpha-helices and adsorb to a hydrophobic surface (desetope) on Ia. By a novel strip-of-helix hydrophobicity algorithm we found that the sequence Leu-142 to His-170 in Ii formed a five-cycle, amphipathic, alpha-helix, the highest scoring one among a series of proteins commonly used as experimental antigens. This finding led to the hypothesis that this sequence in Ii bound to the antigen-binding site (desetope) of Ia until release and self-aggregation in the endosome in order that digested foreign peptides could then bind to Ia. Abundant expression of Ii in leukemic cells might be associated with an altered capacity of those cells to present foreign or leukemic antigens to the host's immune system.

Hydrophobic strip-of-helix algorithm for selection of T cell-presented peptides.

In extension of the hypothesis that an amphipathic alpha helix of Ii (Phe146-Val164) bound to the foreign antigen-presenting site (desetope) of class II MHC molecules through hydrophobic amino acid residues (Phe146, Leu150, Leu153, Met157, Ile160, Val164) which were present in an axial strip along one side of the Ii helix, we developed an algorithm to search for T cell-presented peptides showing a similar hydrophobic strip-of-helix. Such peptides might bind to the class II MHC molecule site which was complementary to the Ii hydrophobic strip-of-helix. The strip-of-helix hydrophobicity index was the mean hydrophobicity (from Kyte-Doolittle values) of sets of amino acids in axial strips down sides of helices for 3-6 turns, at positions, n, n + 4, N + 7, n + 11, n + 14, and n + 18. Peptides correlating well with T cell responsiveness had: (1) 12-19 amino acids (3-5 cycles or 4-6 turns of an alpha helix), (2) a strip with highly hydrophobic residues, (3) adjacent, moderately hydrophilic strips, and (4) no prolines. The degree of hydrophilicity of the remainder of a putative antigenic helix above a threshold value did not count in this index. That is, the magnitude of amphipathicity was not judged to be the principal selecting factor for T cell-presented peptides. This simple algorithm to quantitate strip-of-helix hydrophobicity in a putative amphipathic alpha helix, allowing otherwise generally hydrophilic residues, predicted 10 of 12 T cell-presented peptides in seven well-studied proteins. The derivation and application of this algorithm were analyzed.

A simple provider-based educational intervention to boost infant immunization rates: a controlled trial.

We sought to determine if a simple educational intervention initiated at the first well-child care visit, with reinforcement at subsequent visits, can improve inner-city infant immunization rates. We conducted a controlled trial involving 315 newborn infants and their primary caregivers in 3 inner-city primary care centers. Child health care providers gave caregivers in the intervention group an interactive graphic card with verbal reinforcement. At later visits, stickers were applied to the card when immunizations were given. Routine information was given to controls. After the trial, age-appropriate immunization rates at 7 months were 58% in each group. Intervention infants had 50% fewer missed opportunities to immunize (p=0.01) but cancelled 77% more appointments (p=0.04) than controls. We conclude that a brief educational intervention at the first well-child care visit did not boost 7-month immunization rates, although it was associated with fewer missed opportunities to immunize.

Methylxanthine treatment of smooth muscle cells differentially modulates adenylate cyclase responsiveness.

The DDT1 MF-2 smooth muscle cell line was used to study regulation of the A1 and A2 adenosine receptor (AR)-adenylate cyclase system by two different methylxanthines. 3-isobutyl 1-methylxanthine (IBMX) is both an AR antagonist and a phosphodiesterase inhibitor, while xanthine amine congener is an AR antagonist without phosphodiesterase activity. Incubation of cells for 18 hr with 100 microM IBMX produced a significant (P less than .05) decrease in the basal, isoproterenol- and sodium fluoride-stimulated adenylate cyclase activity. This generalized decrease in adenylate cyclase activity was associated with a significant decrease in the quantity of alpha s (Gs) as determined by Western blotting. In contrast, no alteration in alpha i (Gi) was observed in these same membranes. A significant increase in both the quantity of A1AR and the receptors' affinity for agonist occurred; however, no alteration in the ability of an A1AR selective agonist to inhibit adenylate cyclase activity was observed. Treatment for 18 hr with 50 nM xanthine amine congener, conversely, resulted in an increase in basal and isoproterenol stimulated adenylate cyclase activity with no change in membrane alpha s (Gs). With IBMX, there was an increase in agonist affinity for the A1AR without an associated change in the effect of adenosine agonists on adenylate cyclase activity. These data indicate that methylxanthine analogs which lack the ability to inhibit phosphodiesterases regulate receptor-mediated transmembrane signaling systems quite differently from those possessing such characteristics. The more prototypic methylxanthines regulate both receptors and G proteins in these smooth muscle cells.

Determining immunization rates for inner-city infants: statewide registry data vs medical record review.

OBJECTIVE: This study evaluated the benefit of consulting a statewide immunization registry for inner-city infants whose immunizations appeared, after single-site chart review, to have been delayed. METHODS: We prospectively enrolled 315 newborns in 3 inner-city pediatric clinics. When the infants turned 7 months old, we obtained immunization data from clinic charts and the state registry. RESULTS: On the basis of chart review, 147 infants (47%) were assessed to be delayed in their immunizations; of these, registry data revealed that 28 (19%) had received additional immunizations and 15 (10%) were actually up to date. CONCLUSIONS: A statewide registry can capture immunizations from multiple sources, improving accurate determination of immunization rates in a mobile, inner-city population.

An hypothesis on the binding of an amphipathic, alpha helical sequence in Ii to the desetope of class II antigens.

When we investigated the hypothesis that amphipathic alpha helical peptides digested from foreign antigen bind to class II major histocompatability complex (MHC) molecules' binding site (desetope) for foreign antigen to be presented to T cell receptors, we found such an extended amphipathic helix in Ii. This amphipathic helix was hypothesized to bind Ii to class II MHC antigens until release in endosomes containing digested foreign antigen. Then these amphipathic Ii polypeptides might polymerize so as not to compete with foreign antigen for binding to class II MHC molecules. Various structural models were consistent with these views and led to the suggestion of specific forms of polymeric interaction.