# Neopterin as a Tool for Primate Ecoimmunology: Current Knowledge, Practical Application, and New Directions From Captivity to the Wild

## TL;DR

Neopterin is a useful biomarker for studying immune responses in primates, especially in conservation and welfare contexts, and this review provides practical guidelines for its use.

## Contribution

This review provides best-practice guidelines for using neopterin as a biomarker in primate ecoimmunology, emphasizing practical application and new research directions.

## Key findings

- Neopterin can be reliably measured in urine, enabling frequent sampling in both captive and wild primates.
- Environmental, life-history, and sex-contextual factors influence neopterin levels, making it a valuable tool for ecoimmunological studies.
- Best-practice guidelines for sample collection, storage, and analysis are proposed to improve the reliability of neopterin measurements.

## Abstract

Neopterin is a well‐established biomarker of interferon‐gamma‐mediated macrophage activation that indicates cell‐mediated immune system responses in humans. Because it is readily quantifiable in urine, it is increasingly used in nonhuman primates to study cell‐mediated immune functioning in relation to infectious diseases, but also environmental and individual factors, in both captive and wild primates. This review synthesizes our current knowledge on these topics with a focus on nonhuman primates. We cover the influence of various methodological factors during sampling and analysis on the reliability of neopterin measurements and give practical advice on how these factors can be mitigated. Furthermore, we address the advantages and disadvantages of different biological matrices in which neopterin can be measured and propose best practice guidelines for handling and storage of samples that consider challenges encountered during fieldwork. We conclude this review with an outlook on topics within primatology where neopterin, as a marker of cell‐mediated immune functioning, could become a valuable tool to answer applied questions and test evolutionary hypotheses about immune functioning in primates.

Neopterin is a sensitive and specific biomarker of intracellular pathogen infection and chronic inflammation, and affected by environmental, life‐history, and sex‐contextual factors. This review offers best‐practice guidelines and practical advice on sample collection, storage, and analysis in primates when used for ecoimmunological conservation and welfare questions.

Neopterin is a sensitive and specific biomarker of cell‐mediated immune activation, responsive to intracellular pathogens and chronic inflammation, and affected by environmental, life‐history, and sex‐contextual factors.It can be reliably quantified in urine, allowing frequent sampling in captive and habituated wild primates. This review offers best‐practice guidelines and practical advice on sample collection, storage, and analysis.Neopterin provides a valuable tool for primate ecoimmunology, for investigations of immune responses and trade‐offs in ecologically relevant contexts and can help to evaluate conservation and welfare interventions.

Neopterin is a sensitive and specific biomarker of cell‐mediated immune activation, responsive to intracellular pathogens and chronic inflammation, and affected by environmental, life‐history, and sex‐contextual factors.

It can be reliably quantified in urine, allowing frequent sampling in captive and habituated wild primates. This review offers best‐practice guidelines and practical advice on sample collection, storage, and analysis.

Neopterin provides a valuable tool for primate ecoimmunology, for investigations of immune responses and trade‐offs in ecologically relevant contexts and can help to evaluate conservation and welfare interventions.