Immune System

Immune System (Immunological factors)

The immune system’s job is to defend against infectious organisms and other invaders. It involves a complex biological system involving cells, tissues and organs that all work together to achieve this goal.

The gut lining is one example of an area where protection occurs, and is needed. The cells there sit in ‘stand by’, ready to respond to any intestinal infection or insults to the intestinal lining. When such an attack occurs, the inevitable protective response is inflammation.

The key factor that differentiates individuals with IBD from normal individuals is the ability to ‘turn off’ this response and return to a normal state. By contrast, this process leads to harm in individuals with IBD as they are unable to ‘turn off’ their immunological reactive response.

On a technical note – Immunity explained

The body’s defence against disease causing agents can be grouped into two broad areas:

  • Non-specific resistance (first and second line)
  • Specific resistance or immunity

Non-specific resistance

  • Comprises a wide variety of body reactions that provide immediate responses to fight invasion by a whole range of pathogens (disease causing agents).
  • Defence ‘tactics’ are non-specific in that they are not specifically directed against a particular type of invader. Within non-specific immunity, the body has two lines of defence.
  • The first line of defence includes: skin (provides a physical barrier), and mucous membranes (mucous lubricates and moistens the cavities surface. Because mucous is thick and sticky, it traps many microbes and foreign substances).
  • When pathogens penetrate the physical and chemical barriers of the skin and mucous membranes, they encounter a second line of defence. The second line of defence relates to internal defences: antimicrobial proteins, phagocytes (phago = eat; cytes = cells]; neutrophils and macrophages) killer cells (lymphocytes), inflammation and fever.

Inflammation, one of the key markers of IBD, is a non-specific, defence response of the body to stress and tissue damage. Inflammation is characterised by redness, pain, heat, swelling and loss of function.

Specific resistance OR immunity

  • Involves the production of specific types of cells or specific antibodies to destroy a particular antigen.
  • An antigen is any substance, such as microbes, foods, pollen, or tissue that the immune system recognises as foreign.
  • Two types of cells participate in immune responses:
    • B-cells develop into plasma cells and protect against disease by producing antibodies
    • T-cells attack and destroy foreign cells and microbes