Detection of immunoglobulin light chain restriction by rna in situ hybridization

A method for detecting immunoglobulin light chain restriction and clonality in B cells, the method comprising:

• (a) obtaining a sample of B cells from a subject;
• (b) conducting one or more in situ hybridization assays on the sample using (i) at least one probe set which is designed to specifically hybridize to immunoglobulin kappa chain constant region (IGKCR) RNA;
• (ii) at least one probe set which is designed to specifically hybridize to immunoglobulin lambda chain constant region (IGLCR) RNA;
• and (iii) at least one probe set which is designed to specifically hybridize to immunoglobulin lambda-like polypeptide 5 (IGLL5) RNA;
• (c) detecting signal associated with hybridized IGKCR probe, signal associated with hybridized IGLCR probe, and signal associated with hybridized IGLL5 probe in a population of B cells in the sample;
• and
• (d) determining a pattern of signal associated with hybridized IGKCR probe, hybridized IGLCR probe, and hybridized IGLL5 probe within individual cells in the B cell population, wherein the pattern of signal within individual cells indicates the presence or absence of light chain restriction and clonality of the B cells.