Antibody-dependent cellular cytotoxicity in poikilotherms

Area of Science:

• Comparative immunology
• Cellular cytotoxicity
• Vertebrate immunology

Background:

• Antibody-dependent cellular cytotoxicity (ADCC) is a key immune mechanism in mammals and birds, mediated by K cells.
• The presence and function of similar cytotoxic mechanisms in other vertebrate classes, like amphibians and reptiles, are less understood.

Purpose of the Study:

• To investigate the cytotoxic capabilities of spleen cells from amphibians (Xenopus laevis, Ambystoma mexicanum) and a reptile (Lacerta viridis).
• To determine if these cells can mediate antibody-dependent lysis in the absence of complement.
• To explore the phylogenetic implications of observed cytotoxic phenomena.

Main Methods:

• Chicken red blood cells were labeled with 51Cr-chromate and treated with rabbit anti-chicken red blood cell serum.
• Spleen cells from Xenopus laevis, Ambystoma mexicanum, and Lacerta viridis were incubated with the antibody-coated target cells.
• Cytolysis was quantified by measuring the release of 51Cr in vitro, without the addition of exogenous complement.

Main Results:

• Spleen cells from Xenopus laevis, Ambystoma mexicanum, and Lacerta viridis effectively lysed antibody-coated chicken red blood cells.
• This lysis occurred in the absence of complement, indicating a complement-independent mechanism.
• Optimal conditions for lysis mediated by Xenopus spleen cells were determined.

Conclusions:

• The study demonstrates a functional homologue of antibody-dependent cellular cytotoxicity (ADCC) in amphibians and reptiles.
• This finding suggests that ADCC-like mechanisms may be conserved across a broad range of vertebrate species.
• The results contribute to understanding the evolutionary history of cellular immune responses.