Innate immunity is the immediate response to a challenge that your body mounts. This happens after injury, negative pathogens, challenging microbes or dangerous chemicals. This can happen within minutes or hours of contact and are not specific to the challenge. In other words, they are not responding with a reaction to that particular strain of bacteria, just a general resistance to any pathogen.
This is not a long-lasting response or defense and is soon enhanced and replaced by the action of the Adaptive Immunity. Innate immunity is carried out at a cellular level by various important body cells such as neutrophils, dendritic cells and macrophages. Even gut flora provides innate immunity, which explains why the worst food poisoning cases occur in individuals with chronic antibiotic use in their history or long-term use of antacids.
These essential immune cells are only just developing in infants, which means that infants have a very weak Innate Immunity response. This is why many infants suffer from Cradle Cap, eczema, colic and bacterial or viral infections.
Innate immunity is the key to initial resistance to infection. Someone who gets chronic illnesses, colds every winter or one Strep throat after another has a compromised innate immune response.