I am only trying to explain  (but could not find any source where the origin of this term has been explained suffficiently)

"Classic IHC"   being  part of < Affinity Histochemistry >:

subspecialties:

- Immunohistochemistry = detection of proteins (GP's=glycoproteins) by the binding of the specific antibody to the antigen

- Lectin histochemistry = detection of mono-, di-, tri-, i polysaccharides in the complex molecules by binding of lectins to the saccharides  

- In situ hybridization = detection of specific sequence of nucleoids in DNA or m-RNA by the binding of complementary chain of probe.

Ligand binding assay (affinity histochemistry)

IMHO contrary to that:

IHC staining methods can be classified as immunofluorescence, immunoenzymological staining and affinity histochemistry (cf: http://www.sinobiological.com/immunohistochemistry-ihc-staining.html )

cf. also:  

Combination of immunological and lectin reactions in affinity histochemistry: proposition of the term affinitin.  by  Franz H, Bergmann P, Ziska P. ; Histochemistry. 1979 Feb 21;59(4):335-42. [ http://www.ncbi.nlm.nih.gov/pubmed/429209 ]

or

Immunohistochemistry: A Revolutionary Technique in Laboratory Medicine, by Okoye & Nnatuanya, 2015, Clinical Medicine and Diagnostics 2015, 5(4): 60-69 DOI: 10.5923/j.cmd.20150504.02

[http://www.sapub.org/global/showpaperpdf.aspx?doi=10.5923/j.cmd.20150504.02.]

AFFINITY:  

i) in Biology: A relationship or resemblance in structure between species that suggests a common origin.   or

ii) . Chemistry:

a. An attraction or force between particles or chemicals that causes them to combine.

b. The degree to which particles or chemicals are likely to combine: Hemoglobin has a high affinity for oxygen. Also called avidity.  (just as an e.g.: cf: http://www.thefreedictionary.com/affinity)

Thank you very much.

Merci

Sihem

Dear Sihem, your'e welcome....