What does this study of conjoined twins say about infectious disease, importance of antibodies?

The world population has been (mis)led to believe that antibodies are the most important part of the immune system. We were told that if you have antibodies against a pathogen, you are well protected; if you don't have antibodies, you're highly vulnerable.

Anybody with some basic knowledge of the immune system knows that this is misleading at best, and a total lie at worst. First of all, mucosal and cellular immunity (e.g. T-cells), and other parts of the immune system are absolutely crucial.

Second of all, the amount of antibodies present says almost nothing. If your immune system already knows how to produce the specific antibodies, e.g. because you already have naturally acquired immunity, it can ramp up production very fast. Also, it matters enormously whether the antibodies are neutralizing or not. If they are not neutralizing, they may escort pathogens past the immune system like a Trojan horse, thereby making the disease significantly worse (Antibody Dependent Enhancement, ADE).

The importance of the neutralizing quality of antibodies is almost never mentioned to the public and also not adequately measured.

It seems that the most important reason why so much attention is placed on antibodies, is because they're easy to measure. We should pay attention to what's important, not what's easy to measure.

The book 'Dissolving Illusions' by dr. Susan Humphries and Roman Bystrianyk does a brilliant job of casting doubt on the necessity, safety and efficacy of all vaccines. If I recall correctly, they also mention people who have a genetic disorder which prevents them from making antibodies.

If blood based (humoral) immunity were crucial, these people would be sick continually and probably die young. It turns out that they're perfectly fine. How is this possible? It could for instance be that (1) other parts of their immune system have compensated for their antibody deficiency, or (2) that blood antibodies play no significant role in immunity, or (3) possibly that our whole understanding of immunity and infectious disease is fundamentally flawed.

This video is a segment of a 1957 Russian documentary about Siamese twins. They have connected blood systems, but separate nervous systems. The former is proven for example by injecting only one of the twins with sugar water. Measurements show also the blood glucose levels of the other twin rising shortly after.

Their independent nervous systems is proven by giving only one of the twins a slight pin prick. The one that was pricked starts to cry, while the other stay calm.

This segment shows a case where one of the twins had 39.0°C (102.2°F) fever and pneumonia, and the other had normal body temperature.

If infectious disease was mainly about pathogens being transported by the blood which are combated by antibodies, why does one of the twins get sick but not the other, even though they have a shared blood systems?

NB: The conjoined twins are not socially distancing and not wearing face masks, yet one has a pneumonia and the other doesn't. 🤔

I am no expert in immunology by any stretch, but in the mean time I've learned some essential high level conclusions:

1. The immune system is highly complex. Humans understand many things about this system, but almost nothing in the grand scheme of things. Even the things we do seem to understand, may be wrong. It would be wise for everyone, including or especially the experts, to show much more humility.

2. As the name implies, the immune system is a system of interconnecting parts, just like a gear box of a car. You can't just change one part of the system (such as the antibodies in the immune system or one gear in the gear box) and without affecting other parts, likely in a negative way. Expecting otherwise is highly simplistic and asinine.

3. Even though the theory about vaccinology, immunology and infectious disease seems very advanced, you only need to do some digging to reach points where even the best experts have no clue what's happening and no predictive ability.

See for example the segment at the end of the following video, where an FDA expert is asked a very basic and relevant question about how much spike protein is produced in the human body by the genetic 'vaccines'. The expert answers, "Obviously we don't have a complete understanding of the nature of the way that the vaccine works in terms of producing immune response".
https://rumble.com/v1el1pp

This non-answer is an enormous understatement. The following would be truthful: "Obviously we know almost nothing of the nature how the 'vaccine' works. In the grand scheme of things, we also know almost nothing about the immune system and infectious diseases."

SOURCE
https://www.youtube.com/watch?v=6xW5C326xkc
The original has high quality English translation.