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Histamine plays an important role in the regulation of various immunological functions. To evaluate the role of histamine in contact hypersensitivity, contact dermatitis was induced with dinitrofluorobenzene (DNFB) in histidine decarboxylase knockout (HDC-/-) histamine-deficient and wild-type mice. The DNFB-induced increase of the ear thickness was significantly higher in HDC-/- mice than in wild-type mice. Using flow cytometry, significantly lower percentages of CD4+ Th and CD8+ Tc cells, and significantly higher percentages of CD45R+ B cells were observed in the regional lymph nodes in HDC-/- mice than in wild-type mice. In the ear specimens of both groups, the majority of the infiltrating cells were neutrophils and macrophages at 24 and 48 h after challenge. Using immunohistochemistry, we observed significantly more CD45+ leukocytes in HDC-/- mice than in wild-type mice. The expression of Th1 (IL-2, IFN-gamma, TNF-alpha) and Th2 (IL-4) mRNAs was examined by quantitative real time RT-PCR in the ear samples. The levels of Th1 cytokine mRNAs both at 24 and 48 h after challenge and IL-4 mRNA at 48 h showed a significantly higher increase in HDC-/- mice than in wild-type mice. These results suggest that histamine plays a negative immunoregulatory role in DNFB-induced contact hypersensitivity.

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A novel allergen-specific immunotherapy for IgE-mediated allergies is presented in this paper, using an experimental allergic rhinitis model and a synthetic plasmid pDNA/PEIm nanomedicine expressing ovalbumin as model allergen. Over 50% reduction of symptoms was found as the immune system's balance was favorably altered toward more TH2-polarized immune responses.

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We have reported that, in A/J (A) (H-2a) mice, a partial tolerance to C57BL/10ScSn (B10) (H-2b) skin allografts and a high incidence of lethal lymphoproliferative disorders (LPD) can be induced by the neonatal i.v. injection of 2 x 10(7) semiallogeneic (B10 x A)F1 spleen cells (SC) (Végh, P., Baranyi, L. and Jánossy, T., Cell. Immunol. 1990, 129: 56). In this study, we show that the incidence and mortality of LPD were continuously growing from 1 month of age until the end of the experiment at 1 year (64% and 36%, respectively). Based on histology, 27% of the diseased mice suffered from lymphoid malignancies. In the remaining cases (73%), reactive histopathological changes were seen in the spleen, lymph nodes (LN), liver and kidneys. The proportion of CD4+ T cells in the spleen and LN as well as that of splenic B cells decreased, while the percentages of mature and immature myeloid cells doubled. The total cell number of each (sub)population, however, was elevated in both lymphoid organs. The cells taking part in the lymphoproliferation were of host (A) and not of donor (F1) origin. Preceding the development of apparent LPD, the SC, LN cell and thymus cell suspensions of 1-month-old tolerized mice showed reduced in vitro proliferative responses to T cell and T cell-dependent B cell mitogens (Con A or PWM), while their reactivity to a T cell-independent B cell mitogen (lipopolysaccharide) was essentially unimpaired. This hyporeactivity seems to be functional, because neither histology nor immunophenotyping by flow cytometry revealed significant alterations in the spleen and thymus of such animals, apart from a slight reduction in the ratio of CD4+/CD8+ T cell subpopulations in the spleen. The in vivo T cell-mediated immune response of the tolerized mice was practically normal to third party CBA/Ca (H-2k) allografts. Antithymocyte autoantibodies (ATA) were detected in the sera of 76% of the tolerized mice at 1 month of age (i.e., even before the mass appearance of LPD). ATA as well as antinuclear Ab were present in 65% of the adult tolerized mice, independently of the presence of LPD. Taken together, in A mice neonatally injected with (B10 x A)F1 SC, a partial, specific allograft tolerance and a chronic host-vs.-graft disease-like syndrome developed. The latter is manifested in hyporeactivity to T cell mitogens, development of autoantibodies and, subsequently, in progressive LPD and lymphoid malignancies.

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