Okay, you have a lot of questions there. I'll try to give some answers, but if you want more details or background knowledge I'd recommend you to read /study more about immunology (none of your questions are actually about molecular biology or cell biology).
2) Foreign cells are generally recognised by the immune system, based on the HLA molecules on the ...
Taken from The role of matrix metalloproteinases (MMPs) in the pathophysiology of chronic obstructive pulmonary disease
Metalloelastase (MMP-12) is (as the name suggests) capable of
degrading elastin, as well as other extra-cellular matrix components.
It is produced predominantly by infiltrating macrophages and appears
essential for macrophage ...
I am not sure about what they used in 1958 (perhaps Sorvall). However you may look at recent papers for ECM protein isolation (if that was your objective).
Have a look at this article.
From materials and methods:
ECM protein isolation.
Fibroblasts or A431 cells were removed from the
surface of the culture plate with 2 mM EDTA in PBS for 3–5 min ...
Generally the coating is of poly D-Lysine. Proteases act only on L-amino acids. So, I guess nothing should happen to the usual coated flasks. I have reused the flask even after 2 rounds of trypsinization, and the cells seemed to be fine.
In your case, the matrix is made of proteins isolated from animal sources. They are susceptible to proteolysis. You are ...