T he dendritic cell (DC) plays a central role in orchestrating cellular immune responses to self and foreign antigens. A process of ''maturation'' that occurs after the acquisition of antigen results in up-regulation of MHC͞peptide and costimulatory ligands on the surface of DCs and in the secretion of immunomodulatory cytokines. In the mature state the DC is primed to activate T cells in an antigen-specific fashion. DC maturation is not, however, a consequence of antigen acquisition per se. Exposure to substances within the tissue microenvironment regulate DC maturational events. Among the factors that induce DC maturation are components of pathogenic microorganisms, products secreted by parenchymal cells and macrophages, and contact with activated T cells (1-6). Whether the preservation of DCs in an immature state results from the absence of maturational stimuli or is also actively maintained is not known.We

We have examined the amino-terminal sequence of the Kc light chains of a set of monoclonal antibodies specific for one of the major antigenic determinants (Sb) on the influenza virus PR8[A/PR/8/34(HlNl)J hemagglutinin molecule. This set was believed to be structurally related from earlier serological analysis that typed these K chains as members of the variable (V) region VK21 group [Staudt, L. M. & Gerhard, W. (1983) J. Exp. Med. 157,. Our sequence analysis confirms and extends this conclusion; all examples of this set belong to a subgroup of the VK21 group, V,,21C. A special feature of this set of K light chains is that all examples were derived from the same mouse (designated H36). This sequence analysis along with the characterization of gene rearrangements at the K light chain loci of these hybridomas is consistent with the idea that certain members of this set are the progeny of one or two lymphocytes. Because of this potential clonal relationship, we can reach several conclusions about the diversity observed among these K light chains: (') the diversity is due to somatic mutation, (it) somatic mutations occur sequentially and accumulate in the first complementarity-determining region, and (iii) the extent of somatic variation in this sample is high, suggesting a somatic mutation rate of about 10-3 per base pair per generation.Antibody diversity arises from several sources. Individuals inherit multiple variable (V) region gene segments for both heavy (VH) and light (VK, VA) chains, joining (J) gene segments (JH, J,, Jh), and diversity (D) gene segments (DH).The initial antibody repertoire of an individual is a product of the combinatorial joining of these gene segments, i.e., V4s with JKS or different VH, DH, and JH combinations, that form complete V1 or VH genes. Errors committed during the process of joining contribute additional diversity to this repertoire (reviewed in ref. 1). Finally, that somatic mutation further amplifies this germ-line repertoire seems to be established (2). The original evidence for somatic mutation favored a model by which point mutations accumulate sequentially during cell division (3). Other models link somatic mutation with specific events during lymphocyte differentiation (4, 5) and propose cataclysmic mechanisms of mutagenesis that introduce multiple amino acid substitutions in one step (6, 7). These models are based on the comparison of V region sequences of independently induced plasmacytoma and hybridoma antibodies to their putative germ-line counterparts. Hence, little can be concluded about the time course of somatic mutation.A better understanding of the nature of somatic mutation can be reached by comparisons of the V genes of a cell lineage. Scharff and colleague have analyzed certain mutants and revertants of the cell line S107 and conclude that the in vitro rate of mutation at the VH gene expressed in this plasmacytoma is significantly higher than that of nonimmunoglobulin genes (8). A possible in vivo analogy is described here: we have initiated a structu...

Eosinophil-derived neurotoxin (EDN) and eosinophil cationic protein (ECP) were isolated from lysates of human eosinophil granules by gel filtration and ion exchange chromatography on heparin-Sepharose. Radioimmunoassay, using monoclonal antibodies, of fractions from the heparinSepharose chromatography showed one peak of EDN activity and two peaks of ECP activity (termed ECP-1 and ECP-2).EDN, ECP-1, and ECP-2 each exhibited heterogeneity in charge and molecular weight when analyzed by two-dimensional nonequilibrium pH gradient electrophoresis and NaDodSO4/PAGE. Digestion of EDN with endoglycosidase F (endo F) decreased its molecular weight and charge heterogeneity. Thus, EDN likely contains a single complex oligosaccharide. Endo F digestion of ECP-1 and ECP-2 decreased the molecular weight of both polypeptides, indicating that both likely contain at least one complex oligosaccharide. Amino acid sequence analyses showed that ECP-1 and ECP-2 are identical from residue 1 through residue 59 and that the sequences of EDN and ECP are highly homologous (37 of 55 residues identical). Both EDN and ECP NH2-termnu*al sequences showed significant homology to RNase, especially in regions of the RNase molecule involved in ligand binding. EDN, ECP-1, and ECP-2 had neurotoxic activity, causing the Gordon phenomenon at doses down to 0.15 ,ug when injected into the cisterna magna; the proteins were comparable in their activities. These results indicate that EDN and ECP are related proteins and suggest that they derived from genes associated with the RNase family.The human eosinophil granule contains several cationic proteins including the major basic protein (1-3), the eosinophil cationic protein (ECP) (4,5), the eosinophilderived neurotoxin (EDN) (6, 7), and the eosinophil peroxidase (EPO) (8). Major basic protein and ECP are potent helminthotoxins (9-11), and major basic protein is toxic to mammalian cells (9, 12). When injected intrathecally into rabbits or guinea pigs, both EDN and ECP, but not major basic protein or EPO, produce the Gordon phenomenon, a neurologic syndrome characterized in the rabbit by stiffness, ataxia, muscle weakness, and muscle wasting (6,7,13 MATERIALS AND METHODSEosinophil Granules. From nine patients with marked peripheral blood eosinophilia, eosinophils were collected by cytapheresis with hydroxyethyl-starch (15). The mean percentage of eosinophils in the concentrate was 79% (range, 64-94%); between 2 x 1010 and 2 x 1011 eosinophils were collected from a single patient. For purification of the eosinophil granules from the large numbers of cells obtained, we used procedures described previously (1-3, 7, 16). The enriched granule fractions were transferred to 2-ml freezing vials (Nunc) and stored in liquid nitrogen for up to 3 years.EDN and ECP Isolation. Frozen granule pellets were thawed, adjusted to pH 3 with 0.1 M HCl, and centrifuged at 40,000 x g for 20 min. Supernatants from the granule extracts were applied to a 1.2 x 48 cm Sephadex G-50 column equilibrated with 0.025 M NaOAc/0.15 M Na...

Androgen has been implicated as a negative regulator of host immune function and a factor contributing to the gender dimorphism of autoimmunity. Conversely, androgen deprivation has been suggested to potentiate male host immunity. Studies have shown that removal of androgen in postpubertal male mice produces an increase in size and cellularity of primary and peripheral lymphoid organs, and enhances a variety of immune responses. Yet, few details are known about the effect of androgen removal on T cell-mediated immunity. In this study, we demonstrate two pronounced and independent alterations in T cell immunity that occur in response to androgen deprivation, provided by castration, in postpubertal male mice. First, we show that levels of T cells in peripheral lymphoid tissues of mice are increased by androgen deprivation. Second, T cells from these mice transiently proliferate more vigorously to TCR- and CD28-mediated costimulation as well as to Ag-specific activation. In addition, androgen deprivation accelerates normalization of host T and B cell levels following chemotherapy-induced lymphocyte depletion. Such alterations induced by androgen deprivation may have implications for enhancing immune responses to immunotherapy and for accelerating the recovery of the immune system following chemotherapy.

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Actin reorganization at the immunological synapse is required for the amplification and generation of a functional immune response. Using small interfering RNA, we show here that dynamin 2 (Dyn2), a large GTPase involved in receptor-mediated internalization, did not alter antibody-mediated T cell receptor internalization but considerably affected T cell receptor-stimulated T cell activation by regulating multiple biochemical signaling pathways and the accumulation of F-actin at the immunological synapse. Moreover, Dyn2 interacted directly with the Rho family guanine nucleotide exchange factor Vav1, and this interaction was required for T cell activation. These data identify a functionally important interaction between Dyn2 and Vav1 that regulates actin reorganization and multiple signaling pathways in T lymphocytes.

Nuclear factor B (NF-B) is an inducible transcription factor that regulates genes important in immunity and inflammation. The activity of NF-B is highly regulated: transcriptionally active NF-B proteins are sequestered in the cytoplasm by inhibitory proteins, IB.

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