Category Archives: Molecular Biology Genetic Disorders and Immunology


Acrocentric. Term used to describe a chromosome in which the centromere lies close to one end, producing one long and one short arm. Allele (allelomorph). Alternative form of a gene occupying the same locus on a particular chromosome. Aneuploid. Any chromosomal number that is not the exact multiple of the normal haploid number. Autosome Any chromosome that is not a sex chromosome or mitochondrial chromosome;

Diagnostic tests in clinical immunology

The major investigations in the diagnosis and monitoring of disorders of the immune system are described below. Autoantibodies A characteristic feature of many autoimmune disorders is the presence of specific autoantibodies. These may be useful markers of disease activity, and in monitoring response to therapeutic inventions. Indirect immunofluorescence (IIF) This technique is used to detect organ- and tissuesp


An autoimmune disease occurs when the immune system fails to recognize the body’s own tissues as ‘self and mounts an attack on them. Disorders include rheumatoid arthritis, juvenile (insulin-dependent) diabetes, thyroiditis and multiple sclerosis. Illnesses are divided into those that affect just one organ (organ-specific) and those which affect many systems (organ non-specific or multi-systemic,.

Hypersensitivity diseases

Hypersensitivity reactions underlie a number of autoimmune and allergic conditions. The classification of these reactions . Type I reaction (reaginic/anaphylactic/immediate hypersensitivity reaction) This is an allergic reaction produced within 30 min of exposure to a specific allergen. Allergens, e.g. house dust, pollens, animal danders or moulds, only elicit reactions in certain genetically predisposed i


IMMUNODEFICIENCIES The most severe immunodeficiencies are those that affect both B and T cell responses. These can stem from a variety of defective mechanisms in lymphocyte function, but tend to have rather similar clinical features, combining the opportunist infections of cell-mediated immunodeficiency with those of antibody deficiency. Severe combined immunodeficiency (SClD) This typically presents in the f


X-linked hypogammaglobulinaemia There is a profound reduction in all immunoglobulin classes; B cells and plasma cells are reduced. The defect is in the differentiation of pre- B cells into B cells; T cells are normal. It typically presents with infections, e.g. meningococcal meningitis, mycoplasmal infections, after the first 3-6 months of life, when the protection from pass ively transferred maternal antibod


Neutropenia Congenital neutropenias are rare and, if severe, are often fatal at an early age. Most however are relatively benign and may even be incidental findings. They generally reflect defects of maturation and release of neutrophils from marrow. Staphylococcal skin infections are common manifestations. A particular variant is cyclical neutropenia with cycles of 3-5 weeks, but this disorder is typically 

The immune system in disease

Some diseases due to immunological abnormalities are common in clinical practice, for example rheumatoid arthritis, thyroid disease and allergy. Immunodeficiency is relatively rare, but the occurrence of certain infections in the context of specific immune defects can illuminate the physiological role of those parts of immune defence in control of infection. Immunodeficiency General principles Infection is th

The immune system In concert

Following an antigenic stimulus, the components of the immune system cooperate to meet and eliminate the challenge. The foreign antigen is picked up by a cell of the monocyte/macrophage series and the antigen is degraded or processed and presented to both the Band T lymphocytes. T-helper cells are generated which enhance the antibody response made by B cells. Some of this augmentation is due to secreted lymph

Immune recognition and cellular function

The hallmark of the immune response is its ability to react specifically to given antigen. The mechanism at the heart of this reaction is the way in which antigen is trapped, processed and recognized as foreign. Accessory cells Several cell types, sometimes termed accessory cells, facilitate the antigen-presenting process. Macrophages and monocytes (mononuclear phagocytes) These cells are distributed through