The treatment regimen has improved, so the patients have almost normal life today compared to 30 years ago. The risk of mother-to-children is also lower today, thanks to advancement in medicine.

But WHO is concerned on HIV resistance to some antiretroviral drugs

Further, we have PrEP so the spread is much reduced.

So, less transmission risk in combination with improved antiretroviral therapies gives us MUCH fewer people die from AIDS, making HIV to appear less deadly than what probably is.

Thanks for the answer!

In short, when the ligand (can be peptides, drugs, proteins, etc.) binds to receptor, the said receptor will change its form ("conformational change") and allowing some kinds of actions, i.e. opening ion channel, releasing some kinds of intracellular molecules (second messenger system), increasing/decreasing transcription of some genes, etc.

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Some ligands can be highly specific to its receptor, but some ligands may act at many different receptors. The ligands can bind irreversibly or reversibly, allowing different duration of action and concentrations affecting how the receptor works. Some ligands may also compete for same space of receptor, allowing it to act in dose-dependent manner.

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References:

1. Katzung BG. Basic and Clinical Pharmacology. 14th ed. New York: McGraw Hill Education; 2018.

2. Whalen. Lippincott Illustrated Reviews: Pharmacology (Lippincott Illustrated Reviews Series) SEVENTH EDITION. Vol. 53, Journal of Chemical Information and Modeling. 2019.

Addition: sometimes, the receptor might not do something directly. Instead, it activates second messenger (intracellular messenger) that may do something, e.g. like what you found on GPCR.

Curious question: does superconductor have absolutely nil resistance or the resistance is just too low to measure with available techs?

Isn't it the main purpose of explosive lens? To compress separate sub critical masses into critical mass?

Thanks again for your reply!

That's something new for me. Thanks!

Side question though, can fish absorb oxygen with the swim bladder?

Thanks again for your excellent reply!

Never knew that. Thanks!

Thanks for your excellent reply!

Coincidentally, the paper you cited also explained how isolated situs inversus may form; I'm really grateful you posted the link.

Feel free to correct my understanding: As my understanding, lung did not evolve from gill; rather, it's a structure unrelated to gill and innervated differently and recurrent laryngeal nerve then repurposed to innervate various structures on mammalian neck instead.

And urea requires less water for excretion, something important when you're living on land. Although urea requires more energy, it's excretion is safer and conserves water.

Also, around 10% of kidney nitrogen excretion is in the form of ammonia (in normal conditions)

Further read: Urea excretion in humans

You're right. For some, the reaction is mild, but for some others it can be dangerous. That's why it requires close medical supervision, in case something goes wrong.

Just adding to your reply. I found this paper outlining different, competing hypotheses, and parasite hypothesis is only one of them:

The evolution of IgE-mediated type I hypersensitivity and its immunological value

Me too! I needed to open my immunology textbook to answer this question. It's nice to review and revise knowledge

Gross oversimplification: After being exposed to allergen, your body creates memory of it. First exposure is usually mild, you may not even notice it. But your body creates memory as a defense mechanism. Next time you're exposed to allergens, your body gives stronger and quicker response. That's why your allergy reaction can be worse with time.

With desensitization, you're exposed to allergens in such a small dose that you're not reacting to it. Desensitization tricks your body into thinking that the allergen is just a normal thing in environment and you tolerate (desensitized?) the allergens better with time. Of course this is not possible (yet) for every allergens and you should be under close supervision in case something goes wrong and you have severe reaction.

Immunology is really complex but amazing science field.

PS: if you're interested, probably you should search for "Type I (IgE-mediated) hypersensitivity".