Immunity system complexity: specific organ protections (Introduction)

by David Turell , Friday, July 23, 2021, 05:53 (1009 days ago) @ David Turell

The brain is especially well-protected:

https://www.sciencemagazinedigital.org/sciencemagazine/23_july_2021/MobilePagedArticle....

"Cugurra et al. (Display footnote number:2) demonstrate in a mouse model a pathway by which the central nervous system (CNS) bypasses this circulatory patrol system and supplies the meninges (the membranes that enclose the brain and spinal cord) with functionally distinct myeloid cells through channels that traverse the skull bone marrow. Moreover, Brioschi et al. demonstrate that the meninges are also populated with B cells directly derived from skull marrow hematopoiesis. These studies show that the brain is an immunologically distinct organ that is surrounded by its own cadre of immune cells.

***

"...recent animal studies have demonstrated that these skull-meninges connections have a much more dynamic role, and under pathological conditions such as stroke, they serve as highways for myeloid cells to quickly transmit from skull marrow to the brain parenchyma (Display footnote number:4). Cugurra et al. expand these findings to demonstrate that even under homeostatic conditions, the skull marrow directly supplies myeloid cells to the meninges. These meningeal myeloid cells act as sentries of the brain, poised to respond to the first sign of perturbation.

***

"The authors observed that monocytes that infiltrated the spinal cord or optic nerve in these models were primarily derived from CNS-marrow, suggesting that the meningeal monocytes preferentially protect the organ that it borders. Furthermore, gene expression analysis between CNS-marrow-derived versus bloodderived infiltrating monocytes in EAE reveal that blood-derived monocytes were more enriched for proinflammatory pathways, suggesting differential roles for these monocytes in pathological conditions.

"Brioschi et al. also show that the skull marrow supplies the meninges with B cells in mice. These meningeal B cells mature in the dura and learn to recognize and tolerate CNS antigens. However, in aging mice, the meninges become populated with antigen-experienced, aged B cells derived from the peripheral circulation that have the potential to disrupt the balance of the distinct CNS immune milieu.

"Cugurra et al. and Brioschi et al. suggest that the brain is distinct in having a direct bone marrow pipeline of immune cells to the borders of the brain (see the figure). Although other organs such as heart, lungs, and visceral organs do not have this selective pipeline, it is often forgotten that all these organs do have an organized structure or reservoir of immune cells at their borders. In 1906, the omentum, which covers the visceral organs, was referred to as “the policeman of the abdomen” because it attenuates peritonitis and improves surgi-cal wound healing (Display footnote number:6). Areas on the omentum called milky spots contain immune cells that can promote angiogenesis (Display footnote number:7) and tissue repair (Display footnote number:8).

***

"Having a pool of mature immune cells surrounding an organ provides a critical, immediately available reservoir of specific immune cells. For example, recruitment of monocytes from bone marrow to tissues where they become mature macrophages to initiate repair could take days, especially if new vasculature needs to be constructed. By contrast, a population of mature monocytes in the CNS, or mature GATA6+ macrophages in visceral cavities, are poised to instantly respond to brain, heart, or lung injury."

Comment: Let's concentrate on the brains protections. This is obviously a purposeful design. The brain is so important it should have immediate strong protections, built-in all around it. Chance mutations are not going to find this necessary, since they are not drive by designing thoughts. Only purposeful design creates this.