29 - immunity - definitiosn. Nonspecific and specific immunity. Types of immunopathological reactions. characteristics of immunity in childhood

define immunity

• Complex of physiological processes whose function is to preserve the constancy of the internal environment of the body. It protects the body from all forgein endogenous and exogenous factors

Types of immunity

• nonspecific - innate

• Specific - adaptive

Nonspecific immunity

• Provides general protections

• First line of defence - mechanical and chemical barriers - skin, mucous membrane, saliva, enzymes, secretory immunity

• Second line of defense - non-specific inflammatory reaction. It represents reversible damage of the tissue

• Phagocytosis - a mechanism for destruction of pathogens

• Natural ‘‘killer cells’’ - they destroy tumour and virus cells by cytolysis

Specific immunity

• Third line of defence - mechanisms that recognise body-specific pathogens

• Specific immune reactions are two types:

1. Humoral immune response

2. Cellular immune response

• This types of immunity takes longer to respond

• This type of immunity has memory

Types of immunopathological reactions

1. Type 1 (immediate anaphylactic hypersensitivity)

2. Types 2 (cytotoxic hypersensitivity)

3. Type 3 (immune complex hypersensitivity)

4. Type 4 (delayed - type hypersensitivity)

1. Type 1 (immediate anaphylactic hypersensitivity)

• Involves IgE antibodies and mast cells

• Example - allergic reactions like hay fever, asthma ot anaphylaxis

• Mechanism - upon exposure to allergen, IgE antibodies bind to mast cells, causing the release of histamine and other inflammatory mediators

1. Types 2 (cytotoxic hypersensitivity)

• Involves IgG or IgM antibodies that target cells or tissues

• Example - autoimmune haemolytic anaemia or transfusion reactions

• Mechanism - antibodies bind to the surface of cells, leading to their destruction through complement activation or phagocytosis

1. Type 3 (immune complex hypersensitivity)

• Involves the formation of immune complexes (antigen-antibody complexes)

• Example - systemic lupus erythematosus (SLE) or rheumatoid arthritis

• Mechanism - immune complexes deposit in tissues, triggering inflammation and tissue damage

1. Type 4 (delayed - type hypersensitivity)

• Involves T cells (specifically CD4+ and CD8+ T cells)

• Example - contact dermatitis (e.g. poison ivy) or tuberculosis (TB) skin test reactions

• Mechanisms - T cells respond to antigen-presenting cells, leading to inflammation and tissue injury

Autoimmune reactions

• The body produces antibodies against its own cells and antigens

• Eg. Dermato Bullous - a group of dematoses characterised by blisters and bullae in the skin and mucous membrane

What is intrauterine development

• Passive immunity from mother and its own development of immunoreactivity protects the fetus from congenital infections

Characteristics of immunity in newborns (3-6 months)

• maternal antibodies begin to reduce from the second month of infancy and disappear within 6 months

• Children are retained linger when breastfed, and breastfeeding is the best way to shape the immune phenotype as the milk contains immune cells, growth factors, IgA and cytokines

• Oral mucosa adapts as a barrier

• More difficult recovery from infections and low productivity of lymphoid tissue

Characteristics of immunity in infants (6-12 months)

• The infant is now more in contact with the external environment

• First viral infections are - chickenpox, rubella, respiratory, bowel and herpes

Characteristics of immunity in child (1-3 years)

• child is now in more contact with adults and is more exposed to a variety of infections

• Serum interactions are weak and the antibody concentration is low