Immunodeficiency and its type

  • Immunodeficiency diseases are condition where the defense mechanism of the body is impaired lading to repeated microbial infections of varying severity and sometimes enhanced susceptibility to malignancies.
  • In this condition the system fails to protect the host from disease causing agents or from malignant cells.
  • Deficiency of defense mechanism may include:

a) Specific immune functions – humoral immunity, cell mediated immunity or both.

b) Nonspecific immune functions –phagocytes, complement system which augment and actin conjunction                     with specific immune response.

  • Immunodeficiency are mainly of two types .They are:

 

1.Primary immunodeficiency/ genetic deficiency/ congenital deficiency

2.Secondary immunodeficiency/ acquired immunodeficiency

 

1.Primary immunodeficiency

  • A condition resulting from a genetic or developmental defect of the immune system is called primary immunodeficiency.
  • Most of the primary immunodeficiency are inherited thus called genetic deficiencies or congenital deficiencies.
  • A primary immunodeficiency affects either adaptive or innate immune function.
  • In adaptive immunodeficiency T cell, B cell or both components are involved whereas in innate immumodeficiency, phagocytes or complement factors are involved.
  • Primary immunodeficiency can be categorized as:

Image result for immunodeficiency                       Image result for immunodeficiency

a)Lymphoid immunodeficiency

b)Complement deficiency

c)Phagocytosis deficiency.

a)Lymphoid deficiency

  • It may involve T cells, B cells or both.
  • In B cells deficiency (Humoral deficiency), there appears complete absence of mature reticulating B cells, plasma cells and Ig.
  • This type of disorder have diverse spectrum of disease.
  • Patients with these disorders are usually subjected to recurrent bacterial infection but display normal immunity to most viral and fungal infections because the T cell branch of the immune system is largely unaffected.
  • e.g., X-linked agammaglobulinemia, transient hypo hammaglobulinemia of infancy, common variable immunodeficiency, selective immunoglobulin deficiency, Transcobalamin II deficiency.
  • In T cells (cellular deficiency), more severe and persistent infections are noticed than those of B cells defects.
  • Deficiency of T cells is associated with abnormal antibody level because TH cells are involved in the generation and control of antibody synthesis.
  • Abnormalities of T- lymphocyte development results in viral, intracellular bacterial, fungal and protozoan infection rather than acute bacterial infection.
  • e.g., Thymic hypoplasia (Di George syndrome), chronic mucocutaneous candidosis, purine nucleoside phopshorylase (PNP) deficiency.
  • In combined immunodeficiency, both lineages are affected and are generally lethal.
  • The onset of infection begins early in infancy and the prognosis from these infant causes early death unless therapeutic intervention reconstitutes their defective number of option.
  • e.g.,Ataria telangiectasica, Wiskoh- Aldrich syndrome, Swis type agammaglobulinemia, etc.

b)Complement deficiency

  • It results from the defect of complement system.
  • It can be categorized as complement component deficiency and complement inhibitor deficiency.
  • Complement components deficiency have been detected in genetic deficiencies in human.
  • Genetic deficiencies of C10, C1γ, C1s, C4, and C2 component are associated with defects in activation of the classical pathway.
  • This result in increased susceptibility to pyogenic infection.
  • This may be transmitted as autosomal recessive traits.
  • Hereditary agioneurotic edema is due to the genetic deficiency of C1.
  • Deficiency of C3b inactivators has been associated with chronic recurrent pyogenic lesions.
  • This may be transmitted as autosomal dominant trait.
  • C3 deficiency results in defect of both classical and alternative pathways leading to pyogenic infection and in opsonization and phagocytosis.
  • Deficiency of properdin factor results in impaired activation of alternative pathway that results in pyogenic infection.

c)Phagocytic deficiency

  • It may be impaired by either intrinsic or extrinsic defects.
  • Intrinsic disorders may be due to defects within the phagocytic cells such as enzyme deficiency.
  • Extrinsic disorders may be due to deficiency of opsonin antibody, complement or other factors promoting phagocytosis or to the effects of drugs or anti-neutrophil auto-antibodies.
  • Phagocytic dysfunction leads to increased susceptibility to infection ranging from mild recurrent skin infections to overwhelming systemic infection.
  • e.g., chronic granulomatos disease, Job’s syndrome, etc.

Image result for immunodeficiency                            Image result for primary immunodeficiency

2.Secondary immunodeficiency

  • It is the loss of immune function which arises when infection, drugs (like immunosuppressive agents, corticosteroids), nutritional inadequencies, metabolic disorders and malignancies lead to defects in specific and non-specific immunity.
  • These are very common than primary immunodeficiency.
  • Deficiencies of humoral and cellular immune responses may occur secondarily during the course of many diseases process.
  • Various hormonal and metabolic disorders can also result in immune deficiency including anemia, hypothyroidism, diabetes and hypoglycemia.
  • Smoking, alcoholism and drug abuse also depress immune response.
  • The most well-known example of a secondary immune deficiency is the immunodeficiency caused by the human immunodeficiency virus, or HIV.
  • HIV attacks certain cells in the immune system and prevents them from carrying out their proper functions against microbes.
  • When the immune system is sufficiently weakened, infected people catch atypical and severe infections.
  • This is then called the Acquired Immunodeficiency Syndrome, or AIDS. AIDS at this time is often treated by a specialized multidisciplinary team.

Image result for secondary immunodeficiency                           Image result for secondary immunodeficiency

Immunodeficiency and its type

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