Immunology is a notoriously complex field with distinct concepts and terminology. Yet immunologists regularly and effectively collaborate with other researchers, notably clinicians and experts in population health. How does such ‘collaboration without convergence’ work? This paper offers an answer. Immunology exhibits three features that support collaboration in the absence of major consensus on theories, methods, or concepts. These are: a multifaceted target of inquiry, therapeutic aspirations, and a clear interdisciplinary pathway. Building on these features, I sketch a general account of “low-effort interdisciplinarity” and connect this result to recent work on population health.