Immunity and immune system - class-XII

Edward Jenner is known as father of immunology due to his discovery of famous small pox vaccine which was also the first successful vaccine to be developed and helped in the eradication of disease completely. 

The specific defence system has immunity to specific microbes and antigens hence it is a potent body response and can produce humoral ,oral,lymphoid immunity etc.

Passive immunity is the type of immunization when a ready-made antibody is directly given to the patient to protect the body against foreign attack. It can be injected artificially or provided naturally by mother milk (colostrum) or by transferring it to the foetus by the placenta.

• Immunity tolerance, or immunological tolerance, or immune tolerance, is a state of unresponsiveness of the immune system to substances or tissue that have the capacity to elicit an immune response in a given organism or It is the prevention of an immune response against a particular antigen.
• For example, the immune system is generally tolerant of self-antigens, so it does not usually attack the body's own cells, tissues, and organs. However, when tolerance is lost, disorders like autoimmune disease or food allergy may occur.
  
• Hence Immunity tolerance is developed by interaction with the antigen.
• So, the correct answer is 'Interaction with the antigen'.

Immunity is said to be passive when antibodies produced in other organisms (their sera) are injected into a person who already has a potential antigen in his body. Administration of antibody against tetanus, botulism etc. makes large amounts of antitoxin immediately available to neutralize the toxins.

Protective mechanical barriers include skin, hair, mucus etc. Skin has an outer tough layer made of a protein keratin and is almost impermeable to germs.

Innate immunity also called natural or native immunity. This immunity is by virtue of genetic constitutional make-up. It is there in the body without any external stimulation or a previous infection.

Innate immunity also called natural or inborn immunity. Innate immunity refers to nonspecific defense mechanisms that come into play immediately or within hours of an antigen's appearance in the body.

IgG is the only class of antibodies that can cross the placenta from the mother to the fetus, providing passive immunity to the newborn.

Humans have two types of immunity i.e., innate and acquired immunity. Innate is non specific immunity and acquired is specific immunity.

Rabies is a disease that shows its symptoms in two stages. During $2-10$ days symptoms like hallucination, hydrophobia, seizure and paralysis occurs. Lowered immunity is the symptom of AIDS.

The immune system provides both the types of immune response innate and acquired immune responses. Innate immunity occurs naturally due to genetic factors or physiology. It is a native immune response that present by birth. It provides physical barrier such as skin, Physiological barriers such as pH of the stomach, bile juice, saliva and tears, cellular barriers such as leucocytes, macrophage cell and cytokine barrier.

The innate immune is an older evolutionary defense strategy  and it is dominant immune system response found in plants ,fungi,insects,and primitive multi-cellular organisms..The innate leukocytes includes:

Immunomodulation is modulation (regulatory adjustment) of the immune system. Homeostasis in the immune system, whereby the system self-regulates to adjust immune responses. Immunomodulators are a part of immunotherapy, in which immune responses are induced, amplified, attenuated, or prevented according to therapeutic goals.

Active immunity occurs when the body produces its own antibodies in response to an antigen. Recovering from a natural infection like mumps triggers the body's immune system to create memory cells and antibodies, which is natural active immunity.

Non-specific (innate) immunity includes physical barriers and phagocytes like Kupffer cells, alveolar macrophages, and neutrophils. Lymphocytes (T and B cells) are the primary components of specific (adaptive) immunity.

A- Helper T cells are arguably the most important cells in adaptive immunity, as they are required for almost all adaptive immune responses. They not only help activate B cells to secrete antibodies and macrophages to destroy ingested microbes, but they also help activate cytotoxic T cells to kill infected target cells.

Non-specific immunity operates fast and it is inherited genetically and it is developed by contact with a pathogen but it does not act as a barrier of defence.

The foetus receives some antibodies from their mother through the placenta during pregnancy and colostrum secreted by mother during the initial days of lactation has abundant antibodies (IgA) to protect the infant. These are the two examples of naturally acquired passive immunity.

Natural acquired active immunity occurs when the person is exposed to a live pathogen, develops the disease, and becomes immune as a result of the primary immune response.

Immunologic tolerance is the state of unresponsiveness of the immune system to substances or tissues that have the potential to induce an immune response. Self-tolerance to individuals own antigen is achieved through central and peripheral tolerance.

Inflammation, a response triggered by damage to living tissues. The inflammatory response is a defence mechanism that evolved in higher organisms to protect them from infection and injury. Its purpose is to localize and eliminate the injurious agent and to remove damaged tissue components so that the body can begin to heal. The four cardinal signs of inflammation—redness (Latin rubor), heat (calor), swelling (tumor), and pain (dolor).

Inflammation is a very prominent response to TNF-α. There are four typical signs of inflammation, erythema (redness), heat, swelling, and pain. These are a consequence of increased blood flow and capillary permeability, the influx of phagocytic cells, and tissue damage. Increased blood flow is caused by constriction of the capillaries that carry blood away from the infected area, and leads to engorgement of the capillary network. Erythema and an increase in tissue temperature accompany capillary constriction. In addition, the permeability of capillaries increases, allowing cells and fluid to leave and enter the surrounding tissue. These fluids have a higher protein content than the fluids normally found in tissues, causing swelling.

One of the best-known chemical mediators released from cells during inflammation is histamine, which triggers vasodilation and increases vascular permeability. Stored in granules of circulating basophils and mast cells, histamine is released immediately when these cells are injured.

Histamine, biologically active substance found in a great variety of living organisms. It is distributed widely. The effect histamine has on blood vessels is crucial to its role in the immune response, which is most clearly observed in inflammation i.e., the local reaction of bodily tissues to injury caused by physical damage, infection, or allergic reaction. Injured tissue mast cells  release histamine, causing the surrounding blood vessels to dilate and increase in permeability. This allows fluid and cells of the immune system, such as leukocytes (white blood cells) and blood plasma proteins, to leak from the bloodstream through the vessel walls and migrate to the site of tissue injury or infection, where they begin to fight the infection and nourish and heal the injured tissues..

So, the correct option is 'Option A'.