Immunology

The word (immunology) is derived from the Latin word (Immunis) which means exempt or describes a state of protection or defense.For a pathogen to cause a disease, it must enter the body in a certain dose that is called the infectious dose, which is influenced by what the pathogen that cause the disease, and the host factors which are represented by his immune system. ➢ So, if the host’s body has a good immune system that can defend it from the invading pathogens, then the host is immunocompetent. ➢ On the other hand, if the immune system is weakened so it cannot defend the host’s body from the invading pathogens (microorganism as corona virus), then the host is immunocompromised

But what if any process has failed in the immune system? This will lead to: ➢ Autoimmunity: When our immunity do not recognize self-cell from non-self-cell So it will destroy our tissue. ➢ Immunodeficiency: when there is no enough number of immune cells or malfunctioning immune cells. ➢ Allergies (Hypersensitivity): when there is excessive response from our immune system to a stimulus.

patient who enters the hospital is considered to have hepatitis until proven otherwise➢ As we know, the innate immune system, which is considered the first line of defense, includes the physical barriers, the antigen presenting cells (APCs) like macrophages, and the complement system. ➢ While the adaptive immune system, which is considered the second line of defense and the specific one, includes B lymphocytes that secrete specific immunoglobulins, and T lymphocytes that are specialized in the cell-mediated immunity. - We cannot get interferons of animal and use them on humans- Because the innate immune system defends nonspecifically against microorganisms, it doesn’t need many genes to be expressed, so with time, the ancestral gene didn’t have any major changes while it was changing to the modern gene, so, not that much of proteins will be needed for the innate immune system to do well. - While in the case of adaptive immune system (the specialized branch), the ancestral gene went through many gene duplications and specializations, so that the modern genes of the adaptive immune system code for much diverse proteins that are needed for the adaptive immune system to do it’s job