Human natural chimerism: An acquired character or a vestige of evolution?

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Analysis on five common classes of human natural chimeras (cytomictical, whole body, fetal-maternal, germ cell, and tumor chimeras) reveals that (1) they initiate only during pregnancy, (2) the most common class are chimeras which contain maternal cells, and (3) the primary mechanisms that are involved in their formation and establishment are still elusive. These classes of natural chimerism, are involved only with maladaptive phenomena such as malignancy and autoimmune diseases and without any documented benefit. A recent review has challenged the accepted dogma that the evolution of immunity is pathogen-directed and asserted that preserving individuality from littering the soma and the germline by conspecific alien cells might have been the original function of the innate immunity. Following this tenet, I propose here that human natural chimerism is a by-product of the new role evolved from primitive components of immunity to "educate" the developing embryo with the armamentarium of effector mechanisms, dedicated to purge the individual from pervasive somatic and germline variants, and is not a vestige of evolution.

Original languageEnglish
Pages (from-to)651-657
Number of pages7
JournalHuman Immunology
Issue number6
StatePublished - 2001
Externally publishedYes

Bibliographical note

Funding Information:
This study is part of the research carried out in the Minerva Center for Marine Invertebrate Immunology and Developmental Biology and was also supported by the NIH (R01 DK54762-OIAI) and the BSF.


  • Cytomictical chimera
  • Dispermic chimera
  • Fetal
  • Germ cell
  • Pregnancy

ASJC Scopus subject areas

  • Immunology and Allergy
  • Immunology


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