Where does imprinting collide?

In the study of animal behaviour, imprinting is a rapid and stable form of learning in which a young animal, during a brief sensitive period soon after hatching or birth, forms a lasting attachment to the first suitable object it meets, usually its parent. Lorenz's 1937 The Companion in the Bird's World described how newly hatched goslings would follow and bond to the first moving thing they saw, whether a mother goose or a person, and would keep that attachment for life; a related version, sexual imprinting, shapes what an adult later finds attractive. What is learned this way resists later change once the sensitive period closes. This referent is a behaviour of a whole living animal, fixed early and lasting, and it has nothing to do with a pattern of gene expression, a bias in the immune system, or a shape pressed into a polymer.[1]

Unit

One animal's early-fixed attachment to an imprinting object

Recovery means

Largely irreversible: what is imprinted during the sensitive period resists later relearning

Measured by

Assessed by following behaviour and preference tests during and after the sensitive period

In genetics and epigenetics, imprinting is a pattern of gene expression in which a gene is switched on or off according to whether it was inherited from the mother or the father, so that only one parent's copy is active. Surani, Barton, and Norris's 1984 experiment on reconstituted mouse eggs showed that the maternal and paternal genomes are not equivalent, and Reik and Walter's 2001 review Genomic imprinting: parental influence on the genome set out how chemical marks laid down while eggs and sperm form carry this parent-of-origin memory. Faults in these marks cause disorders such as Prader-Willi and Angelman syndromes. This referent is a molecular labelling of DNA passed between generations, not a young animal's attachment, an immune bias, or an industrial stamping process.[2][3]

Unit

One gene or locus expressed from only a single parental copy

Recovery means

Reset each generation: marks are erased and rewritten in the germline

Measured by

Detected by allele-specific expression assays and by mapping DNA methylation at imprinted loci

In immunology, imprinting, long called original antigenic sin, is the immune system's tendency to lean on memory from its first encounter with a pathogen when it later meets a related variant, sometimes at the cost of a weaker response to the new threat. Francis named the doctrine in 1960, and Zhang, Stacey, Mullarkey, and Miller's 2019 review of original antigenic sin traced how a person's first influenza exposure shapes their antibody responses for life. This bias can blunt the protection given by later infections or vaccines against drifted strains. This referent is a property of an immune repertoire skewed by first exposure, unrelated to a gosling's bond, a parent-of-origin gene, or a moulded surface.[4][5]

Unit

One immune repertoire biased toward its first antigen exposure

Recovery means

Persistent: the first-exposure bias tends to recur when a related variant appears

Measured by

Measured by antibody titres and specificity against the original strain versus newer variants

In chemistry and materials science, molecular imprinting is a way of making a polymer that remembers the shape of a target molecule: the molecule serves as a template while the polymer forms around it, and once it is washed out it leaves behind a cavity that selectively rebinds molecules of the same shape. Wulff's 1995 review Molecular Imprinting in Cross-Linked Materials with the Aid of Molecular Templates: A Way towards Artificial Antibodies set out how such templated cavities act as synthetic recognition sites. The result is used for sensors, separations, and artificial antibodies. This referent is a shape recorded in a synthetic solid, not a behaviour learned by an animal, a mark on inherited DNA, or a bias in the immune system.[6]

Unit

One templated binding cavity in a cross-linked polymer

Recovery means

Not applicable

Measured by

Assessed by rebinding assays, selectivity coefficients, and binding-site characterisation