I am doing my thesis corrections, and my examiner (an engineer) has different ideas about whether the word should be pluralised than those I am used to, as I am a non-biochemist, I wanted advice on the accepted practice.

When talking about multiple types of antibody I am used to people in my lab saying antibodies, however as my lab is very international I realise that the way we talk may be idiosyncratic.

e.g. "within the polyclonal serum we found antibodies against a number of targets";

but when we are talking about antibody of one type we use the singular;

e.g. "the pipette contained 25mg/ml of SN607D8 antibody"


"the pipette contained 25mg/ml of SN607D8 antibodies".

Is this correct? Are there any documents that lay out the grammar for such things?

Similarly when we are talking about multiple types of antigen we say antigens

"the antibody bound specifically to HLA-A2, but non specifically to a number of other antigens";

but when we are talking about a number of a single type of antigen we would use the singular

"the cell had numerous HLA-A2 antigen on its surface"


"the cell had numerous HLA-A2 antigens on its surface".

Again is this correct?

  • You're arguing that the question should be on a science site. / I've science degrees, so I'll add my opinions on how to handle the pluralisation issue later. – Edwin Ashworth Jun 4 '19 at 11:18
  • It seems "English Language and Usage" also gets plenty of questions about writing mathematics, writing computer code, and so on. So why would we object to a question about writing biology? – GEdgar Jun 4 '19 at 11:56

(1) Words used to describe agglomerations, like 'soup'and 'gravy', can often be used in either non-count or count mode:

"I've got soup on my shirt." [private communication]


'Our hearty, easy-to-make Knorr gravies come in a variety of delicious flavours.' [Knorr® advert]

With antibody, the same behaviour is found:

'the pipette contained 25mg/ml of SN607D8 antibody'

[non-count usage]


'within the polyclonal serum we found antibodies against a number of targets' [count usage, the plural form being used for 'types of antibodies']


(2) A real complication arises however with how some terms, like antibody and antigen, are used. While we don't talk of a 'soup particle' or a 'gravy molecule', antibodies and antigens are etically discrete, and usage seeks to allow for this while failing to differentiate senses. While Webster's New World College Dictionary, 5th Edition has:

antibody noun pl. -bodies

a specialized protein produced by certain lymphocytes

(and we'd speak of a protein molecule, not of course a protein, when meaning a single molecule)

YourDictionary has:

antibody noun

The definition of an antibody is a protein molecule that can be found in the blood and ...

and RHK Webster's has

antibody n pl. -bodies

  1. any of numerous protein molecules produced by B cells as a primary immune defense, each kind having a uniquely shaped site that combines with a foreign antigen, as of a virus or bacterium, and disables it.

licensing 'antibody' to be used interchangeably with 'individual antibody molecule'. This is a second count usage, and this situation is more confusing than the corresponding situation with say coffee ('The two coffees grown are arabica and robusta' v "Two coffees, please!") or cat ('Jaguars and pumas are two less well-known cats' v 'Two cats were fighting in the street').

With 'virus', the situation is clarified by using the term 'virion' for a single entity. The situation really needs rationalising elsewhere.


In general, both the terms– antibody and antigen, refer to classes of functional biomolecules (with the former being more specific) and are seldom used to mean individual molecules. The plural form denotes the different types.

"within the polyclonal serum we found antibodies against a number of targets"

This usage is fine. However, when referring to polyclonal antibody against a particular protein (not epitopes), you just use the singular form even though it is a mix of different monoclonal antibodies. For e.g. polyclonal antibody against actin. In this case, the term antibody refers to the formulation.

"the pipette contained 25mg/ml of SN607D8 antibody"

This is correct as it refers to the concentration of a specific antibody.

"the cell had numerous HLA-A2 antigen(s) on its surface".

Both usages are incorrect. Again, this statement uses the term antigen to describe different copies of the same molecule. In case of HLA, you should use the term MHC/HLA receptors if you want to indicate the different protein molecules/complexes on the cell surface. You can also use the term copies to mean many molecules of the same type. When you want to talk about HLA polymorphism you should use the terms variants or alleles.

You can use the plural form to describe different types of antigens. For e.g. the bacteria has several antigens on its cell wall.

  • 1
    "An antigen refers to an epitope." could you clarify? My understanding was that an epitope is a region on the surface of the antigen where the antibody binds. – Abijah Jun 4 '19 at 13:16
  • @Abijah "antigen" means something that can bind to an antibody. It is an archaic term. By that statement, I meant that antigen doesn't mean a protein molecule. It means some molecular entity that can elicit an immune response by binding to an antibody. You are right: epitope is a part of the molecule that the antibody binds. I'll clarify – WYSIWYG Jun 4 '19 at 13:24

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