I’m a little rusty on this aspect but I’ll try to explain how things work which may help you answer things better for yourself. we have multiple antibody types making up our immune system. Some of these cells are in constant rotation and react to a broad range of things, they are first line of defense. There are also antibodies for specific antigens and these can take time to make, if you’ve never had exposure to a disease it would take the body a little extra time to ramp up and attack. Some immune cells have longer memories and can be stored away in our lymph nodes until needed leading to a faster response.

The stuff we have vaccines for are diseases that our body makes the memory cells for. Viruses like the one that causes flu constantly change their surface proteins over time which is why we need new ones so frequently, we don’t have the cells to fight the new strains. Some infections can completely wipe out immune systems memory leaving us more vulnerable as we have no/limited immune memory and would have to rebuild it.

There is no way to generally enhance, though limiting stress etc will help your cells do their jobs better in mounting a defense.