Search

It has been well established that T cells can recognize small mol. wt compounds such as drugs. Results from previous studies revealing a high heterogeneity and cross-reactivity of drug-specific T cell clones (TCC) in individual patients prompted us to analyze the degeneracy of drug-reactive TCR in detail. Hence, we analyzed the MHC restriction pattern of a panel of 100 drug-specific TCC isolated from different drug-allergic donors. We found that 28 of the tested clones showed an MHC allele-unrestricted drug recognition. Most of these clones were at the same time highly drug specific, i.e. they could only be stimulated by the original drug and not by any drug derivatives. In contrast, TCC with the ability to interact with different drug derivatives displayed a clearly MHC allele-restricted drug recognition. Therefore, we concluded that the TCR of these clones is mainly interacting with side chains of the appropriate drug molecules and hence able to tolerate alterations in the MHC molecule. Moreover, we tested all clones for additional alloreactivity and found that 27 clones could be stimulated by a self-MHC-peptide-drug complex as well as by a non-self-MHC-peptide complex. This cross-reactivity with allogeneic MHC molecules was substantially higher in drug-specific TCC compared to tetanus toxoid-specific clones from the same donors. This suggests that from the point of view of drug-specific TCR, non-self-MHC-peptide complexes have a higher incidence to mimic the `original' self-MHC-peptide-drug complex and this may occur for TCR recognizing self-MHC-pathogen-derived peptide complexes. Finally, the biological functions of bispecific TCC were not influenced by the nature of the stimulating ligand. Both drug as well as allogeneic stimulation led to similar reaction patterns in the analyzed TCC.

It has been well established that T cells can recognize small mol. wt compounds such as drugs. Results from previous studies revealing a high heterogeneity and cross-reactivity of drug-specific T cell clones (TCC) in individual patients prompted us to analyze the degeneracy of drug-reactive TCR in detail. Hence, we analyzed the MHC restriction pattern of a panel of 100 drug-specific TCC isolated from different drug-allergic donors. We found that 28 of the tested clones showed an MHC allele-unrestricted drug recognition. Most of these clones were at the same time highly drug specific, i.e. they could only be stimulated by the original drug and not by any drug derivatives. In contrast, TCC with the ability to interact with different drug derivatives displayed a clearly MHC allele-restricted drug recognition. Therefore, we concluded that the TCR of these clones is mainly interacting with side chains of the appropriate drug molecules and hence able to tolerate alterations in the MHC molecule. Moreover, we tested all clones for additional alloreactivity and found that 27 clones could be stimulated by a self-MHC--peptide--drug complex as well as by a non-self-MHC--peptide complex. This cross-reactivity with allogeneic MHC molecules was substantially higher in drug-specific TCC compared to tetanus toxoid-specific clones from the same donors. This suggests that from the point of view of drug-specific TCR, non-self-MHC--peptide complexes have a higher incidence to mimic the 'original' self-MHC--peptide-drug complex and this may occur for TCR recognizing self-MHC--pathogen-derived peptide complexes. Finally, the biological functions of bispecific TCC were not influenced by the nature of the stimulating ligand. Both drug as well as allogeneic stimulation led to similar reaction patterns in the analyzed TCC.

The T cell co-stimulatory receptors CD28 and CTLA-4 appear to have opposite effects on T cell activation, mediating augmentation and inhibition of T cell responses respectively. Since these two receptors use the same ligands, CD80 (B7-1) and CD86 (B7-2), the co-ordinate timing of CD28 and CTLA-4 expression has a major impact on the regulation of immune responses. While the kinetics of co-stimulatory molecules have been established for T cell stimulation in vitro, little is known about CD28 and CTLA-4 expression in response to T cell activation in vivo. In this study we have investigated the kinetics of CD28 and CTLA-4 expression upon CD4⁺ T cell activation in response to soluble peptide in vivo. Using mice transgenic for a T cell receptor specific for the I-A^u-restricted N-terminal peptide of myelin basic protein MBP Ac1-9, we show maximal up-regulation of both CD28 and CTLA-4 2 days after peptide administration. CTLA-4 expression correlated positively with early activation markers on the same cells and was high on blast cells. Administration of peptide analogs with higher affinity for I-A^u MHC class II revealed a higher increase in CTLA-4 than in CD28 expression in response to improved TCR ligation. Further, a small population of CD4⁺ T cells expressing CTLA-4, CD25 and CD45RB^low was identified in mice that had not been treated with specific peptide. The implications of these observations for immune regulation are discussed.

Experimental autoimmune encephalomyelitis (EAE) is a CD4⁺ T cell-mediated, inflammatory disease with similarities to multiple sclerosis in humans. Intranasal (i.n.) administration of a myelin basic protein (MBP)-derived peptide can protect susceptible mice from EAE. The mechanisms underlying this phenomenon, however, remain unclear. To analyze the phenotypic and functional changes taking place during the induction of tolerance by peptide inhalation, we have studied the fate of CD4⁺ T cells after i.n. peptide application using transgenic mice expressing a TCR specific for the N-terminal peptide (Ac1-9) of MBP. Peripheral T cell death was variably observed in TCR transgenic mice after a single i.n. administration of antigenic peptide but was transient and incomplete. Transgenic spleen cells and cervical lymph node cells responded with a cytokine burst to peptide inhalation and hyperproliferation when re-stimulated in vitro. Transfer experiments demonstrated that the duration of peptide administration required to induce tolerance depended on the precursor frequency of T cells in recipient animals. The stringency of i.n. peptide treatment was increased so as to test the efficacy of tolerance induction both in vitro and in vivo in the presence of high precursor frequencies of antigen-specific T cells. Multiple i.n. doses of peptide completely protected TCR transgenic mice from EAE induced with myelin. Such repeated peptide administration resulted in down-regulation of the capacity of antigen-specific CD4⁺ T cells to proliferate or to produce IL-2, IFN-γ and IL-4 but increased the production of IL-10. The role of IL-10 in suppression of EAE in vivo was demonstrated by neutralization of IL-10. This completely restored susceptibility to EAE in mice previously protected by i.n. peptide. Considering the immunosuppressive properties of IL-10, T cells which are resistant to apoptosis might act as regulatory cells and mediate bystander suppression.

We studied the reactivity of T and B cells against a soluble form of the glycoprotein of vesicular stomatitis virus (VSV-G) which was expressed in a transgenic mouse (line 23) under the control of the hormone regulated β-lactoglobulin promoter. Transgenic mice expressed VSV-G in the thymus, spleen, mammary gland and lung. VSV-G transcripts in the thymus varied with age, i.e., expression was high early in life and decreased with age. VSV-G transgenic mice immunized with recombinantvacciniavirus expressing VSV-G exhibited normal VSV-G-specific IgM levels, but a 30-fold reduction in IgG response, indicating functional VSV-G-specific B cell activity but impaired T helper cell responses. Interestingly, VSV-G-specific T helper cell activity was reduced only early (4–10 weeks) and late in life (>40 weeks) but was normal in between. Double transgenic mice expressing VSV-G and a VSV-G-specific TCR (line 23×7) demonstrated that TCR transgenic CD4+T cells were partially deleted in early life, but then gradually repopulated the periphery and remained constant. These findings suggest that in line 23 two different mechanisms regulated levels of the immune response: clonal reduction/deletion of VSV-G-specific T cells during early life followed by peripheral anergy at a later stage.

The neutralizing immunoglobulin M (IgM) response to vesicular stomatitis virus (VSV) has been shown to be largely T-cell independent in several T-cell-deficient models of mice. By using different antigen froms of VSV, VSV antigen doses could be graded in vivo (infectious > > UV inactivated > formalin inactivated). The present study reveals a T-cell-dependent component of the neutralizing IgM response in nude mice given intravenous injections of low doses of noninfectious UV-inactivated VSV serotype Indiana (VSV-IND) only if the mice are transfused with VSV-IND-specific helper T cells. Instead, nude mice immunized with infectious VSV, which leads to greater antigen doses in vivo, were able to mount an IgM response in the absence of T cells. These results indicate that the IgM response to low doses of VSV-IND glycoprotein (G) is T-cell dependent. Nude mice immunized with infectious VSV also made a variable but low VSV-IND-neutralizing IgG response. A VSV-IND matrix (M)-specific helper T-cell line rendered this response more consistent, much higher, and longer lasting. Thus (i) VSV-G induces a mostly T-cell-independent but partially T-cell-dependent IgM (the latter can be visualized best at low doses of antigen) and (ii) the antibody response to VSV in nude mice proceeds through steps, i.e., IgM and IgG, that are dose dependent. The results suggest that the predominant role of helper T cells may be to expand and maintain the individual steps of differentiating B cells.

The T-helper (Th) cell epitopes in the glycoprotein (GP) of vesicular stomatitis virus serotype Indiana (VSV-IND) were analyzed with a complete panel of overlapping synthetic peptides. Three Th-cell epitopes in C57BL/6 (H-2b) mice and two epitopes in BALB/c (H-2d) mice were defined by their ability to stimulate in vitro proliferation of virus-primed, CD8+ T-cell-depleted spleen cells in a class II-restricted manner. A series of CD4+, I-Ab-restricted T-cell hybridomas from VSV-primed C57BL/6 mice were characterized by their production of interleukin-2 and interleukin-3 upon stimulation with VSV-IND or purified VSV GP in vitro. Of nine hybridomas derived from three independent fusions, five were specific for amino acids (aa) 415 to 433 (p8) of VSV-IND GP, three recognized aa 52 to 71 (p41), and one reacted against aa 316 to 335 (p17). Fluorocytometric analysis of Th hybridomas or VSV-stimulated T-cell lines with monoclonal antibodies specific for the T-cell receptor V beta chain did not reveal obvious correlations between the T-cell receptor V beta gene segment used and the epitope recognized. All three peptides recognized by H-2b mice and both epitopes recognized by H-2d mice which were characterized in primed T-cell populations were capable of activating specific Th cells in vivo as measured by the induction of antibody class switch from immunoglobulin M (IgM) to IgG. Thus, the epitopes are relevant for VSV GP-specific Th response in vivo and are able to provide functional help for the production of anti-VSV-specific neutralizing IgG antibodies.

Histochemical stainings of head louse nits were performed and observations indicated that the nit sheath was nonchitinous. One discernable membrane composed of hyaluronic acid was established that encircled the larvae within the egg. The structural framework of the egg included a definite lattice around each aeropyle of the operculum, through which oxygen exchange occurred.

Pediculosis affects more elementary school students than all other communicable childhood diseases combined, excluding the common cold. The current study using scanning electron microscopy visualized operculums through which developing embryos received oxygen, as well as fracture lines within the adherent sheath by which the egg is attached to the hair. Using microscopic techniques, including freeze-fracturing, the mode of attachment of the sheath to the hair follicle was observed, in addition to the existence of several inner membranes enclosing the embryo within the egg structure. The chemical nature of the sheath is also analyzed using electron dispersive x-ray analysis.