[scientizscht (OP)]

If you inject a human enzyme in a human, will it cause immunological reaction?

I know you can eat enzymes from microbes etc.

But if you inject them, will they induce immunological response?

[evan_au]

Your body recognises many molecules as "self", and will not have circulating antibodies to these molecules. These "self" molecules essentially consist of proteins that are normally present on the surface of your own cells.

So if you take one of your own proteins or enzymes that are normally only present inside a cell, and release them outside a cell, it is possible that there will be circulating antibodies that will bind to it.

But it normally takes some inflammation or damage to activate the immune system, and create a strong immune response.

The serious problems occur when some environmental influence causes the immune system to see some normal surface proteins as being dangerous, and it then goes around destroying any cells displaying these proteins. This is thought to trigger type 1 diabetes and other auto-immune diseases in susceptible individuals.
See: https://en.wikipedia.org/wiki/Autoimmune_disease