Characterization of interleukin-1 activity in tunicates

Area of Science:

• Immunology
• Marine Biology
• Evolutionary Biology

Background:

• Interleukin-1 (IL-1) is a key immune signaling molecule in vertebrates.
• The evolutionary origins and conservation of IL-1 across diverse taxa are not fully understood.
• Tunicates, as basal chordates, offer a unique model to study ancient immune mechanisms.

Purpose of the Study:

• To investigate the presence and characteristics of IL-1-like activity in North American tunicate species.
• To determine if tunicate immune molecules exhibit functional conservation with vertebrate IL-1.
• To explore the molecular properties and biological activities of these tunicate-derived factors.

Main Methods:

• Screening of eight North American tunicate species for IL-1-like activity.
• Utilizing G50 column chromatography to separate molecular species based on weight.
• Assessing lymphocyte activation factor (LAF) activity and mitogenic effects on thymocytes.
• Evaluating induction of vascular permeability in rabbit skin assays.
• Neutralization assays using polyclonal anti-human IL-1 antisera.

Main Results:

• All eight tunicate species examined exhibited detectable lymphocyte activation factor (LAF) activity.
• Chromatography separated distinct molecular weight fractions with varying biological activities.
• Fractions with LAF activity induced increased vascular permeability, a known IL-1 effect.
• Tunicate LAF activity was effectively neutralized by antibodies against human IL-1.

Conclusions:

• Tunicates produce molecules with significant interleukin-1 (IL-1) like activity.
• These findings demonstrate that IL-1 is an ancient molecule with conserved functions across a wide evolutionary range.
• The study supports the hypothesis of IL-1's deep evolutionary roots and its fundamental role in immune responses.