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Modulation of IL-1 alpha, IL-1 beta, and 25K Mr non-IL-1 activity released by human mononuclear cells
C I Sandborg1, M A Berman, K L Imfeld
1Department of Medicine, California College of Medicine, University of California, Irvine 92717.
Abstract:
To determine if the release of IL-1 alpha and IL-1 beta by cultured PBMC could be independently modulated by different exogenous stimuli, we examined the effect of LPS, IFN gamma, latex beads, and indomethacin on the release of IL-1 alpha and IL-1 beta. PBMC culture supernatants were fractionated by Sephacryl-S-200 column chromatography or HPLC (TSK G3000SW), and each fraction was tested for thymocyte mitogenic activity in the presence or absence of preincubation with anti-IL-1 alpha or anti IL-1 beta monoclonal antibody (mAb) and for the presence of IL-1 alpha or IL-1 beta protein by ELISA. In all experiments, thymocyte mitogenic activity not neutralizable by anti-IL-1 alpha or anti-IL-1 beta mAb was detected in the 25K Mr range, which ranged from 12 to 50% of the total thymocyte mitogenic activity released, depending on the stimuli. Cultured PBMC from 95% of individuals release thymocyte mitogenic activity in the absence of exogenous stimuli, which was increased 1.3-to 7-fold by lopopolysaccharide (LPS) (25-50 micrograms/ml). All of this increased activity was due to increased release of IL-1 beta and non-IL-1 thymocyte mitogenic activity, with no change in the total amount of IL-1 alpha released. Indomethacin (0.1 microgram/ml) induced release of increased thymocyte mitogenic activity of 1.3- to 1.4-fold over unstimulated cultures. All of this increased activity was due to increased release of IL-1 alpha and non-IL-1 activity with a concomitant decrease in IL-1 beta release. Interferon gamma (40-100 U/ml) increased the amount of IL-1 alpha and decreased IL-1 beta and non-IL-1 activity released, resulting in no overall change in the total amount of thymocyte mitogenic activity. Molecular weight fractionation of the PBMC culture supernatants revealed that thymocyte mitogenic activity eluting in the 25K Mr range was not due to IL-1 alpha or IL-1 beta. With certain culture conditions, thymocyte mitogenic activity was detected in the 30-40K Mr range. PBMC cultured with LPS and latex beads in the absence of serum released 30-40K Mr IL-1 alpha, as well as 17K Mr IL-1 alpha and 17K Mr IL-1 beta. PBMC cultured in 2% fetal calf serum (FCS) alone from some donors released only 30-40K Mr thymocyte mitogenic activity. Both IL-1 alpha and IL-1 beta protein was detected by ELISA in this Mr range but only the IL-1 alpha was bioactive.(ABSTRACT TRUNCATED AT 250 WORDS)
Insights
Different stimuli independently modulate Interleukin-1 alpha (IL-1 alpha) and Interleukin-1 beta (IL-1 beta) release from peripheral blood mononuclear cells (PBMC). This study reveals distinct effects of lipopolysaccharide (LPS), interferon gamma (IFN gamma), and indomethacin on IL-1 alpha and IL-1 beta production.
Area of Science:
- Immunology
- Cell Biology
- Molecular Biology
Background:
- Interleukin-1 alpha (IL-1 alpha) and Interleukin-1 beta (IL-1 beta) are key cytokines involved in inflammatory responses.
- Peripheral blood mononuclear cells (PBMC) are a primary source of IL-1 production.
- Understanding the independent modulation of IL-1 alpha and IL-1 beta release is crucial for targeted immunomodulation.
Purpose of the Study:
- To investigate whether exogenous stimuli differentially regulate the release of IL-1 alpha and IL-1 beta from cultured PBMC.
- To characterize the nature of thymocyte mitogenic activity in PBMC culture supernatants under various stimulation conditions.
Main Methods:
- Cultured PBMC were stimulated with lipopolysaccharide (LPS), interferon gamma (IFN gamma), latex beads, and indomethacin.
- Supernatants were analyzed using Sephacryl-S-200 column chromatography and HPLC for thymocyte mitogenic activity.
- ELISA and monoclonal antibody (mAb) neutralization assays were employed to quantify IL-1 alpha and IL-1 beta.
Main Results:
- LPS increased IL-1 beta and non-IL-1 mitogenic activity, without altering IL-1 alpha levels.
- Indomethacin elevated IL-1 alpha and non-IL-1 activity while decreasing IL-1 beta release.
- IFN gamma enhanced IL-1 alpha but reduced IL-1 beta and non-IL-1 activity, leading to no net change in total mitogenic activity.
Conclusions:
- The release of IL-1 alpha and IL-1 beta by PBMC can be independently modulated by distinct exogenous stimuli.
- A significant portion of thymocyte mitogenic activity in PBMC supernatants is not attributable to IL-1 alpha or IL-1 beta.
- Specific molecular weight fractions (e.g., 30-40K Mr) contain bioactive IL-1 alpha, and potentially IL-1 beta, depending on culture conditions.