My immediate thought upon reading this was that, contrary to Scott's expectation, I would bet that bisexuals are quite likely to be immunologically different. Specifically, both the immune system and sexuality are potentially influenced by or correlated with levels of testosterone and estrogen.
For example, high estrogen makes people prone to more severe manifestations of all sorts of illnesses associated with an overactive immune system because estrogen causes histamine release. Testosterone, on the other hand, tends to act as a mast-cell stabilizer and suppresses the immune system. In line with this theory, homosexual men often have higher testosterone than straight men according to a few studies, which could explain their unusually low long covid rate (I remembered the association off the top of my head, but here's a small study I just found with a brief search showing "significantly higher" testosterone in homosexual men: https://ajp.psychiatryonline.org/doi/10.1176/ajp.131.1.82 )
Unfortunately for my theory, I haven't been able to find any studies on the average hormone profiles of bisexual men, and at least based on this this meta-analysis: https://link.springer.com/article/10.1007/s10508-020-01717-8 bisexual women have at best slightly higher testosterone than average, though the abstract itself says that most studies on the topic have been "small, biased, and heterogenous" and that little confidence should be placed in their findings.
My immediate thought upon reading this was that, contrary to Scott's expectation, I would bet that bisexuals are quite likely to be immunologically different. Specifically, both the immune system and sexuality are potentially influenced by or correlated with levels of testosterone and estrogen.
For example, high estrogen makes people prone to more severe manifestations of all sorts of illnesses associated with an overactive immune system because estrogen causes histamine release. Testosterone, on the other hand, tends to act as a mast-cell stabilizer and suppresses the immune system. In line with this theory, homosexual men often have higher testosterone than straight men according to a few studies, which could explain their unusually low long covid rate (I remembered the association off the top of my head, but here's a small study I just found with a brief search showing "significantly higher" testosterone in homosexual men: https://ajp.psychiatryonline.org/doi/10.1176/ajp.131.1.82 )
Unfortunately for my theory, I haven't been able to find any studies on the average hormone profiles of bisexual men, and at least based on this this meta-analysis: https://link.springer.com/article/10.1007/s10508-020-01717-8 bisexual women have at best slightly higher testosterone than average, though the abstract itself says that most studies on the topic have been "small, biased, and heterogenous" and that little confidence should be placed in their findings.