There have been decades of research trying to identify biomarkers and structural differences in individuals with neuropsychiatric diseases, using imaging (MRI, fMRI), electrical activity (EEG), or serum markers (blood work) . In major depressive disorder for example, there have been associations made with changes in the prefrontal cortex, thalamus, hypothalamus etc. as seen on MRI. However these findings are neither sensitive nor specific, so psychiatric/behavioral disorders such as MDD is still a clinical diagnosis.

I should make the distinction that there are some psychiatric diseases result from structural diseases of the brain. E.g. Alzheimer's disease, Lewy body dementia, Parkinson's disease, all have distinctive findings on MRI and can have psychiatric symptoms. However most people with psychiatric disorders do not have obvious neurological disease that can be identified with imaging.

There is a lot of research and development in the field, and there is a great effort in psychiatry to incorporate objective measurements to validate clinical findings. So our understanding of neuropsychiatric diseases is likely to change dramatically in the coming years, once we develop the tools to understand these disorders better.

Short answer, yes. Pregnant women are recommended to receive the MMR vaccine BEFORE pregnancy as this confers protection to the developing fetus from rubella infection. Not having immunity to rubella greatly increases the risk of Congenital Rubella Syndrome (CRS) in the fetus if the mother acquires rubella during pregnancy.

The vaccine should be administered before pregnancy since the MMR vaccine is live attenuated virus, meaning there is a small chance of developing a mild version of the disease. Although the symptoms would be mild for the mother, the risk of CRS for the fetus means it is advised to not receive the vaccine during pregnancy.

In terms of immunity, typically people who have completed the full course of MMR as a child are considered to have life-long immunity. Antibody titers do wane over time, so the only way to confirm would be to measure antibody titers with blood work.

Well, yes and no - this will require a bit of a deeper dive into immunology. Our immune system has two general branches, the adaptive (slower but can "learn") and innate (quick but limited to pre-determined common patterns). There isn't a "red list" per se for the innate immune system since it is evolutionarily more efficient for our innate immune cells to have the receptors for the definitely dangerous patterns, and let the adaptive immune system "learn" which patterns are safe.

As a metaphor for the innate immune system, the TSA displays a list of things that are definitely banned on planes. They may not need to have a list of things that are "definitely safe", they can figure that out along the way.

Anyway to return to your question, the adaptive immune system DOES have the ability to identify molecules that are safe. "Mucosal tolerance" refers to the ability of the body to suppress immune responses against antigens that are encountered in the gastrointestinal tract. This is not only to protect the commensal bacteria that live in our intestines, but also prevents our immune system from flaring up against the molecules in our food.

At a very simple level, it's all concentration gradients. Kind of like a dog can sniff and follow a scent trail from a very faint signature, following the trail until it is eventually on top of the target. Immune cells like the one in the video (presumably a monocyte or macrophage) have receptors specifically designed for Pathogen-Associated-Molecular-Patterns (PAMPs). PAMPs are molecules that are found on bacteria, fungi, viruses etc that our immune cells have evolved to recognize with receptors specific to them (antibodies not needed). An example of a PAMP is endotoxin/LPS that is a part of the bacterial cell wall. So for example, the bacteria sheds LPS or other pieces of its cell wall as it floats around, and the immune cell "sniffs" it out with its receptor and starts following the trail.

It gets more complex. There are hierarchical signals for what determines which direction an immune cell will migrate. For example, if local tissue cells realize there is an active ongoing infection, they will secrete "red flag" signals to recruit nearby immune cells to the area. These signals are called chemokines. So the immune cell floating around your blood will first detect the chemokines and realize something is wrong, and will enter the area where they are coming from. From that point on, if it senses PAMPs (the bacterial molecules), it'll switch and start moving toward the bacteria.