In order to determine the role of CD4+ and CD8+ T-cells and of interleukin-5 (IL-5) in causing antigen-induced eosinophil infiltration into the site of airway late-phase reaction, we examined the effect of the in vivo depletion of CD4+ and CD8+ T-cells on the eosinophil infiltration of the trachea induced by antigen inhalation in mice. We also studied the effect of anti-murine IL-5 monoclonal antibody (mAb) on the antigen-induced eosinophil infiltration in the trachea. The eosinophil infiltration into the trachea of ovalbumin (OVA)-sensitized BALB/c mice began to increase 9 h after OVA inhalation and persisted for more than 48 h. The in vivo depletion of CD4+ T-cells by pretreatment with anti-L3T4 mAb significantly decreased the eosinophil infiltration induced by OVA inhalation in the trachea of sensitized mice. However, the in vivo depletion of CD8+ T-cells by pretreatment with anti-Lyt-2 mAb had no significant effect on OVA-induced eosinophil infiltration in the trachea. Pretreatment with anti-murine IL-5 mAb also decreased OVA-induced eosinophil infiltration in the trachea. In contrast, neither disodium cromoglycate nor a selective antagonist for platelet-activating factor CV-6209 decreased OVA-induced airway eosinophilia in the mouse. Our results provide direct evidence that CD4+ but not CD8+ T-cells mediate antigen-induced eosinophil recruitment in the airways and that IL-5 mediates this eosinophil recruitment.

Previous studies suggested that the eosinophil recruitment into the site of cutaneous late-phase reaction (LPR) was dependent on IgE antibody and mast cells. In this study, we determined the role of CD4+ T cells and CD8+ T cells in causing antigen-induced eosinophil recruitment of LPR in mouse skin. Eosinophil infiltration into the subcutaneous tissue of ovalbumin (OVA)-sensitized BALB/c mice was biphasic, reaching the first peak at 6 h after the subcutaneous challenge with OVA and the second peak at 24 to 48 h. The in vivo depletion of CD4+ T cells by pretreatment with anti-L3T4 monoclonal antibody (mAb) significantly decreased the second peak (at 24 h and 48 h), but not the first peak (at 6 h), of OVA-induced eosinophil infiltration into the skin of OVA-sensitized mice. However, the depletion of CD8+ T cells by pretreatment with anti-Lyt-2 mAb had no significant effect on either the first peak or second peak of OVA-induced cutaneous eosinophilia. Pretreatment with anti-murine interleukin-5 (IL-5) mAb also decreased the second peak, but not the first peak, of OVA-induced cutaneous eosinophilia. In contrast to the inhibitory effects of depletion of CD4+ T cells and of anti-IL-5 mAb on the second peak of antigen-induced cutaneous eosinophilia, disodium cromoglycate and a selective antagonist for platelet activating factor (PAF) CV-6209 decreased the first peak of OVA-induced cutaneous eosinophilia in the mouse. These results indicate that CD4+ T cells, but not CD8+ T cells, cause the second peak of antigen-induced eosinophil recruitment of cutaneous LPR and that IL-5 mediates this eosinophil recruitment. In contrast, the first peak of antigen-induced eosinophil recruitment of cutaneous LPR is mediated by mast cells and PAF.

No abstract

It has recently been shown that substance P induces neutrophil infiltration in the skin, which is mediated through mast cell degranulation. Since substance P activates both skin mast cells and vascular endothelial cells, we compared the potencies of substance P and a mast cell-degranulating agent, compound 48/80, which is inactive for vascular endothelial cells, in inducing neutrophil infiltration in mouse skin. We also examined the effect of the C-terminal peptide of substance P, SP_6–11, which is active for vascular endothelial cells, on compound 48/80-induced neutrophil infiltration in the skin. Subcutaneous administrations of substance P (10^––7 to 10^––5M; 0.1 ml) and compound 48/80 (0.5-50 μg/ml) induced neutrophil infiltrations and mast cell degranulations in mouse skin in a concentration-dependent fashion. Moreover, substance P induced more neutrophil infiltrations than compound 48/80 in terms of the magnitude of mast cell degranulations. SF_6–11 (10^––6 to 10^––4M) induced no significant neutrophil infiltration or mast cell degranulation, but increased the vascular permeability of endothelial cells in the skin. Furthermore, SP_6–11 enhanced compound 48/80-induced neutrophil infiltration without any increase in mast cell degranulation. Our results indicate that, in addition to mast cell degranulation, the activation of vascular endothelial cells is involved in substance P-induced neutrophil infiltration in the skin.

SUMMARYPrevious studies have shown that substance P induces granulocyle infiltration in mouse skin, which is mediated through mast cell dcgranulation. However, il is not yet known whether the direct etTect of substance P on vascular endotheiiai cells is involved in the granulocyle infiltration in tbe skin. To solve this issue, we used the N-terminal peptide substance P| •> (SPi .,). which is active for mast cells but inactive for vascular endotheiiai eells, and the (-terminal peptide SP^ u. which is active for vascular endotheiiai cells bul inactive for mast cells, since substance P activates bolh mast cells and vascular endotheiiai cells. The subcutaneous administration of substance P(IO '-I0 ''M) caused granulocyte (ncutrophil and eosinophil) infiltration in the skin of BALB/c mice 6 h after ihe injection. SP| «(10 -10 '' M) also caused granulocyte infiltration of mouse skin which was associated with mast cell degranulation. In contrast. SPhu (lO'-IO"* M), whieh was found to increase the vascular permeability of endolhelial cells in mouse skin, induced no significant granulocyte infiltration nor mast cell degranulation. However. SP^ n (10 '-I0 •" M) enhanced SP, ,,-induced granulocyte infiltration in the skin without any significant increase in masl cell degranulation. We conclude thai substance P causes granulocyte infiltration in mouse skin through both mast cell degranulation induced by the N-terminal peptide of substance P and the activation of vascular endotheiiai cells induced by the c-terminal peptide of substance P.