This immunity exists in our body before we born. The innate immunity also called genetic immunity is because of genetically determined characteristics.
But we can also develop immunity later on, which is called adaptive immunity. Just like mothers milk provides some sort of immunity to the babies. Immunization is an artificial way of developing adaptive immunity to particular pathogen of interest.
Theoretically the host defenses of young, healthy, human adults are capable of preventing nearly all infectious diseases but a variety of disorders, injuries, medical interventions and environmental factors alters our resistance to infectious agents, making us prey.
Genetically some people or races of people are resistance to some type of disease/pathogens and other peoples to other disease/pathogens. Generally, very young (infants/neonates or children) and elderly are most susceptible to infections compared to young people. Children below the age of 3 years are more susceptible due to less developed immune system and elderly due to waning of immune system.
- Take special precautions and do not expose yourself unnecessarily to infectious agents. While travelling to public buses, trains etc. and while visiting hospitals use special masks to protect you from getting respiratory pathogens.
- Protect yourself from traumatic injury because traumatic injuries lower our resistance level and at the same time provide easier access for germs to reach to inner tissues.
- Protect yourself from air pollution and exposure to radiation
Pollution and exposure to radiation also lowers resistance to infection. Air pollutants, including tobacco smoke damage respiratory membranes and reduce their ability to remove foreign substances. They also depress the activity of phagocytes.
- Do not take unnecessary antibiotics
Antibiotics destroy commensal organisms which provides various benefits to our body by producing vitamins and also competing with pathogenic microorganisms. Indiscriminate use of antibiotics allows opportunistic infections to become established.
- Get adequate protein and vitamin intake
It helps for maintaining healthy intact skin and mucous membranes and phagocytic activity. It is also important for lymphocyte production and antibody synthesis.
- Have regular moderate exercise
Regular moderate exercise of 30-45 minutes can produce a 20% increase in antibody level, which occurs during exercise and one hour afterwards. At that time Natural Killer cells activity also increased. But excessive exercise eg running more than 20 miles per week depresses the immune system.