I have carried out an ELISPOT with human B cells that were stimulated with R848 (TLR7/8 antagonist) and IL-2 for 7 days prior to being added to the ELISPOT plate coated with goat anti-human IgG antibodies. Upon revelation, I observed these areas of large white circles with areola of blue antibodies? The circles seem too large to be imprints of a cell, even a hyperblastic cell. I am stunned as to what they can be. Has anyone got an explanation or seen anything like this before?

I have attached a photo of the well in question as well as a control unstimulated well for the same donor.