Interleukin-1 beta, but not interleukin-1 alpha, is required for T-cell-dependent antibody production

Abstract

Interleukin-1 (IL-1) consists of two molecules, IL-1 alpha and IL-1 beta, and IL-1 receptor antagonist (IL-1Ra) is a natural inhibitor of these molecules. Although the adjuvant effects of exogenously administered IL-1 in the humoral immune response are well known, the roles of endogenous IL-1 and the functional discrimination between IL-1 alpha and IL-1 beta have not been elucidated completely. In this report, we investigated the role of IL-1 in the humoral immune response using gene-targeted mice. Both primary and secondary antibody production against T-dependent antigen, sheep red blood cells (SRBC), was significantly reduced in IL-1 alpha/beta-/- mice, and was enhanced in IL-1Ra-/- mice. The intrinsic functions of B cells, such as antibody production against type 1 T-independent antigen, trinitrophenyl-lipopolysaccharide and proliferative responses against mitogenic stimuli, were normal in IL-1 alpha/beta-/- mice. The proliferative response of T cells and cytokine production upon stimulation with anti-CD3 monoclonal antibody were also normal, as was the phagocytotic ability of antigen-presenting cells (APCs). However, SRBC-specific proliferative response and cytokine production of T cells through the interaction with APCs were markedly impaired in IL-1 alpha/beta-/- mice, and enhanced in IL-1Ra-/- mice. Moreover, we show that SRBC-specific antibody production was reduced in IL-1 beta-/- mice, but not in IL-1 alpha-/- mice. These results show that endogenous IL-1 beta, but not IL-1 alpha, is involved in T-cell-dependent antibody production, and IL-1 promotes the antigen-specific T-cell helper function through the T-cell-APC interaction.

Figure 1

Efficiency of antibody production against SRBC in IL-1α/β^−/− and IL-1Ra^−/− mice. Mice were immunized with SRBC (arrow point), and sera were collected 1 and 2 weeks after the primary and secondary immunizations. After appropriate dilution of the serum (IgM and IgG: 1/100 dilution), SRBC-specific antibody levels in the sera were measured by ELISA. (a) Wild-type mice: n = 10, IL-1α/β^−/− mice: n = 10. (b) IL-1Ra^−/− mice: n = 7. The average and standard deviation (SD) are shown. *P < 0·05; #P < 0·005.

Figure 2

Intrinsic functions of B cells in IL-1α/β^−/− mice. (a) Mice were immunized with TNP-LPS, and the sera were collected before immunization, and 1 and 2 weeks after immunization. After 1/1000 dilution, anti-TNP-specific IgM levels in sera were measured by ELISA. Wild-type mice: n = 4, IL-1α/β^−/− mice: n = 4. Average±SD is shown. (b) Proliferative responses of splenocytes against mitogenic stimulations were measured by the incorporation of [³H]thymidine using IL-1α/β^−/− mice. Bars represent an average of two or three mice with SD. One representative result from three independent experiments is shown.

Figure 3

Intrinsic functions of T cells in IL-1α/β^−/− mice. Proliferative responses of splenic T cells against plate-coated anti-CD3 monoclonal antibody only or with soluble anti-CD28 monoclonal antibody were measured by the incorporation of [³H]thymidine using IL-1α/β^−/− mice Cytokine levels in culture supernatants were measured by ELISA Bars represent an average of two or three mice with SD. One representative result from three independent experiments is shown.

Figure 4

Phagocytic abilities of APCs of IL-1α/β^−/− mice. Phagocytic abilities of FITC-latex beads and FITC-dextran of PECs and pinocytic abilities for lucifer yellow of SACs from wild-type and IL-1α/β^−/− mice were assessed by flow cytometry. One representative result from at least three independent experiments is shown.

Figure 5

Impaired T-cell responses through T-cell–APC interaction in IL-1α/β^−/− mice. Proliferative responses and cytokine production of antigen-specific T cells upon interaction with SACs were determined. T cells (2 × 10⁵ cells) from the spleen of SRBC-immunized wild-type (WT), IL-1α/β^−/− (Δα/β)(a), and IL-1Ra^−/− (Δra) mice (c) were cultured with SACs from non-immunized mice in the absence (hatched column) or presence (closed column) of soluble SRBC antigen, and the proliferative responses were measured by the incorporation of [³H]thymidine after 5 days. Cytokine levels in the supernatants of the IL-1α/β^−/− mouse (b) or IL-1Ra^−/− mouse (d) T-cell cultures were measured. Average±SD is shown in (a) and (c), while bars in (b) and (d) show the total amount of the cytokine in triplicate culture supernatants. One representative result from three independent experiments is shown.

Figure 6

Efficiency of antibody production against SRBC in IL-1α^−/− and IL-1β^−/− mice. Mice were immunized with SRBC (arrow point), and sera were collected 1 and 2 weeks after the primary and secondary immunization. After appropriate dilution of the serum (IgM and IgG: 1/100 dilution), SRBC-specific antibody levels in the sera were measured by ELISA. (a) Wild-type mice: n = 8, IL-1α^−/− mice: n = 7. (b) IL-1β^−/− mice: n = 7. The average and standard deviation (SD) are shown. *P < 0·05, and #P < 0·005.

Figure 7

Antibody production against type 2 TI antigens in IL-1α/β^−/− mice. Mice were immunized with TNP-Ficoll (arrow point), and the sera were collected 1 and 2 weeks after the primary and secondary immunization. After 1/1000 dilution, anti-TNP-specific immunoglobulin levels in sera were measured by ELISA. Wild-type mice: n = 5, IL-1α/β^−/− mice: n = 5. Average±SD is shown. *P < 0·05, and #P < 0·005.