Specific Detection of Antigen-Binding Cells by Localized Growth of Bacteria

AUTOR(ES)

Rotman, Boris

RESUMO

A new method for the enumeration of lymphoid cells with specific surface-receptors for antigen is described, based on the use of β-D-galactosidase (EC 3.2.1.23), either directly as an antigen or as a conjugated antigen. Binding of β-D-galactosidase is revealed by its activity in releasing riboflavin from a synthetic substrate, riboflavin-β-D-galactopyranoside. The riboflavin, inactive as a vitamin in the galactosidic form, becomes active when released by the enzyme, and can be detected by bioassay. Hence, lymphoid cells with receptors for β-D-galactosidase on their surface can be detected after they have been exposed to the enzyme, washed, and then plated in agar containing riboflavin-β-D-galactopyranoside, streptomycin, riboflavin-deficient medium, and a streptomycin-resistant strain of Streptococcus faecalis that requires riboflavin. Release of riboflavin is signalled by the growth of characteristic bacterial colonies over the cell that bound β-D-galactosidase.

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