Titre (or titer) is the reciprocal of maximum dilution at which you can still reliably detect activity of your antibody. So if you can dilute your starting material 1 in 128 and still reliably confirm activity but at the next dilution point (for example 1 in 256 for a two fold dilution series) you cannot confirm activity, then the titre of that sample is called 128. Obviously you need to define what you regard as a reliable end point determination for your assay which is where a consideration of signal to noise is important. Ideally you'd set the end point so that within statistical error limits you'd rarely get a false positive or negative arising from the assay i.e. if you ran the same sample and the controls many times how often would you get a different result? Obviously the end point or titre of your antibody is dependent on the starting concentration of antibody and also on the affinity (or for multivalent binding the avidity) for antigen. Higher starting concentrations or higher affinity antibodies will give you a higher titre. The measurement of titre is useful in that it allows you to easily compare two or more samples and ask the simple question of which sample appears to have the higher activity of binding and also to quantify the difference as a relative titre e.g sample A might have a titre of 128 and sample B a titre of 32 allowing you to say that A is 4 times more active than B.

Hello Ahmad,

Titer has more to do with the the concentration of antibodies in the spent medium (if the Ab is sceretory). The mAbs produced commercially are extra-cellular in nature and their titer is usually measured using Protein-A affinity chromatorgraphy (HPLC). The definition of good titer differs from one mAb to another. In general any titer between 2-5g/l is considered as good.

The signal to noise ratio has more to do with the instrument and less to do with the process or biological concentration. However, it is definitely needed to maintain a high signal to noise ratio to avoid background error. This is general is true with any instrument used for similar purposes.

regards

Jitendra

Titre (or titer) is the reciprocal of maximum dilution at which you can still reliably detect activity of your antibody. So if you can dilute your starting material 1 in 128 and still reliably confirm activity but at the next dilution point (for example 1 in 256 for a two fold dilution series) you cannot confirm activity, then the titre of that sample is called 128. Obviously you need to define what you regard as a reliable end point determination for your assay which is where a consideration of signal to noise is important. Ideally you'd set the end point so that within statistical error limits you'd rarely get a false positive or negative arising from the assay i.e. if you ran the same sample and the controls many times how often would you get a different result? Obviously the end point or titre of your antibody is dependent on the starting concentration of antibody and also on the affinity (or for multivalent binding the avidity) for antigen. Higher starting concentrations or higher affinity antibodies will give you a higher titre. The measurement of titre is useful in that it allows you to easily compare two or more samples and ask the simple question of which sample appears to have the higher activity of binding and also to quantify the difference as a relative titre e.g sample A might have a titre of 128 and sample B a titre of 32 allowing you to say that A is 4 times more active than B.

Thanks a lot Mike and Jitendra for your inputs.. i totally agree with you mr. Mike !