Compositions and methods including recombinant B lymphocyte cell line including an exogenously incorporated nucleic acid expressing an exogenous membrane immunoglobulin reactive to a first antigen and including an endogenous gene expressing an endogenous secreted immunoglobulin reactive to a second antigen

1. A method for producing an immunoglobulin in an isolated B lymphocyte cell line comprising:

isolating from a vertebrate subject exposed to at least one first antigen, a B lymphocyte cell, and growing the B lymphocyte in vitro to obtain a B lymphocyte cell line expressing at least one endogenous secreted immunoglobulin reactive to the at least one first antigen;

introducing into the isolated B lymphocyte cell line at least one exogenous membrane immunoglobulin reactive to at least one second antigen to produce a recombinant B lymphocyte cell line;

selecting the isolated B lymphocyte cell line expressing the membrane immunoglobulin reactive to the at least one second antigen and expressing the at least one endogenous secreted immunoglobulin reactive to the at least one first antigen.

2. The method of claim 1 comprising:

administering the at least one second antigen to stimulate the recombinant B lymphocyte cell line; and

measuring production of the at least one endogenous secreted immunoglobulin reactive to the at least one first antigen in the recombinant B lymphocyte cell line.

3. The method of claim 1 , wherein introducing into the at least one isolated recombinant B lymphocyte cell line at least one exogenous membrane immunoglobulin reactive to the at least one second antigen comprises introducing at least one exogenous membrane immunoglobulin polypeptide reactive to the at least one second antigen.

4. The method of claim 1 , wherein introducing into the at least one isolated recombinant B lymphocyte cell line at least one exogenous membrane immunoglobulin reactive to the at least one second antigen comprises introducing at least one exogenous nucleic acid encoding at least one membrane immunoglobulin reactive to the at least one second antigen.

5. The method of claim 1 comprising:

exposing the recombinant B lymphocyte cell line to the at least one second antigen to activate the recombinant B lymphocyte cell line to express the endogenous secreted immunoglobulin reactive to the at least one first antigen.

6. The method of claim 5 comprising:

isolating the endogenous secreted immunoglobulin reactive to the at least one second antigen from the recombinant B lymphocyte cell line or from a culture of the recombinant B lymphocyte cell line.

7. The method of claim 1 , comprising:

exposing the recombinant B lymphocyte cell line to the at least one second antigen to activate the recombinant B lymphocyte cell line to express the exogenously incorporated membrane immunoglobulin reactive to the at least one second antigen, wherein activating the at least one exogenously incorporated membrane immunoglobulin with the first antigen is configured to control expression of at least one endogenous nucleic acid encoding the at least one secreted immunoglobulin reactive to the first antigen.

8. The method of claim 1 , wherein

the isolated B lymphocyte cell line comprises at least one of naïve B lymphocytes, immature B lymphocytes, transitional B lymphocytes, mature B lymphocytes, follicular B lymphocytes, memory B lymphocytes, plasmablasts, or plasma cells.

9. The method of claim 1 , wherein

the isolated B lymphocyte cell line comprises at least one memory B lymphocyte.