In your new job with a biotech company, you created a new transgenic mouse strai
ID: 79532 • Letter: I
Question
In your new job with a biotech company, you created a new transgenic mouse strain that you nicknamed “I want a salary increase” (IWASI). IWASI mice constitutively express a transgene encoding a rearranged immunoglobulin heavy chain, whose transcription and translation lead to production of functional B-cell receptors (BCRs) with high affinities for a ubiquitous, murine, cell-surface antigen. In comparison with normal mice, your IWASI mice will very likely display [complete the sentence and assess the resulting statements (7-12) as either factually correct (= true) or incorrect (= false)]: 7. increased numbers of circulating B cells, because they have a growth advantage as a result of not having to rearrange their own immunoglobulin heavy chains. 8. increased apoptosis of bone marrow B cells, because of their autoreactive heavy chain expression. 9. decreased incidence of somatic hypermutation in order to reduce negative effects of autoreactivity of transgenic BCRs. 10. reduced numbers of naïve B cells exiting the bone marrow due to high levels of B-cell death during selection processes. 11. increased B-cell class switching, as a means of replacing the autoreactive heavy chain. 12. increased numbers of positively selected T cells in the thymus as a result of increased T-cell help required for B cells replacing the autoreactive heavy chain.
Explanation / Answer
The main difference between the IWASI mice compared with normal mice it would have
1. increased apoptosis of bone marrow B cells, because of their autoreactive heavy chain expression.
2. reduced numbers of naïve B cells exiting the bone marrow due to high levels of B-cell death during selection processes.
The false statements include
7. increased numbers of circulating B cells, because they have a growth advantage as a result of not having to rearrange their own immunoglobulin heavy chains.
9. decreased incidence of somatic hypermutation in order to reduce negative effects of autoreactivity of transgenic BCRs.
11. increased B-cell class switching, as a means of replacing the autoreactive heavy chain.
12. increased numbers of positively selected T cells in the thymus as a result of increased T-cell help required for B cells replacing the autoreactive heavy chain.