Immunoglobulins are serum proteins having antibody activity. These proteins migrate to gamma globulin region when we do the electrophoresis of serum. These proteins are termed as gamma globulins. The gamma globulin fraction of human serum/plasma contains a variety of immunoglobulins or antibodies. Every molecule of an immunoglobulin carries antibody specificity for a single antigen. Immunoglobulins are produced by the plasma cells, primarily in the bone marrow. Plasma cells present in the germinal centers of lymph-nodes and spleen also produce immunoglobulins. A plasma cell needs activation by a specific antigen to produce immunoglobulins capable of reacting/interacting with thestimulatory antigen. Plasma cells are capable of proliferating into an expanded population or clone of identical cells. A clone of plasma cells produces immunoglobulins/antibodies with identical physical and chemical properties, also known as homogeneous or monoclonal antibodies/immunoglobulins. If more than one antigen is involved, the plasma cells will proliferate to form multiple clones and produce heterogeneous or polyclonal immunoglobulins. Plasma cells release the immunoglobulins in the surrounding tissue and thus immunoglobulins accumulate in our blood and provide immunity against infectious organisms. There are a variety of actions and reactions performed by immunoglobulins.
There are three major classes of
immunoglobulins/antibodies: Immunoglobulin-G (
IgG), immunoglobulin-A (
IgA) and immunoglobulin-M (
IgM). The
IgG is the major Immunoglobulin
class and account for 80% of all
antibodies. Impaired production of
immunoglobulins by the
plasma cells is termed as
immunoglobulins' deficiency or
hypogammaglobulinemia. The
hypogammaglobulinemia may be either
primary (
congenital) or
secondary (
acquired) probably due to some other disorder or
immunosuppressive therapy or
radiation. Primary immunodeficiency (
PID) disorders are most commonly detected in children and secondary
immunodeficiency (
SID) among adults. Frequent and/or unusual infections are an indicator of impaired immune
defenses. The clinician would get to know form the history of the patient, especially a child that he/she has
impaired immune defense. Frequent Streptococcal, Pseudomonas, pneumococcal or influenza infections alerts the physician to work up to rule out the
immunodeficiency in a child or adult patient. An infection history representative of
generalized immunodeficiency differs from
selective immunodeficiency such as
IgA deficiency. Selective
IgA deficiency occurs in 0.1 to 0.2% children having history of sinusitis and pneumonia.
Laboratory Investigations
In addition to detailed clinical history, it is essential to get the following investigations done:
- Serum Electrophoresis: Serum protein electrophoresis (SPE) test
should be done to rule out generalized deficiency or hypogammaglobulinemia.
- Complete Immunoglobulin evaluation: Levels of IgG, IgA and IgM in serum should be determined by single radial immunodiffusion (SRID) method. To rule out selective IgA deficiency, salivary IgA level should also be detected in patient's saliva by SRID assay. While determining immunoglobulin deficiency in infants, it should be kept in mind that their immunoglobulin levels may drop temporarily at third to fifth month of age. Since birth the infant is protected by the maternal immunoglobulins transferred from the mother's blood circulation through placental barrier. The infant's own plasma cells (immune system) get mature around sixth month of age and start producing immunoglobulins. The transient hypogammaglobulinemia during third to fifth month of age should not be confused as PID.
- Ancillary Tests: Following ancillary tests should be done to assess the antibody producing capacity of the patient: i) Titer value of ABO hemagglutinins, ii) Titer value of antistreptolysin-O, and iii) Assay for diphtheria antibodies (Schick test).
Treatment of ImmunodeficiencyIn most instances, immunoglobulin deficiency disorders (IDD) cannot be prevented. However, if diagnosed early enough, these can be treated successfully. Three means of treatment are available to the physician to manage immunoglobulin deficiency disorders (IDD):
- Prophylaxis from infectious agents: Proper immunization of the infants is must as per W.H.O. protocol for immunization
- Antibiotic therapy: Appropriate antibiotic therapy should be administered through appropriate route depending on the condition of patient.
- Gamma globulin replacement therapy: If a patient has severe infection which is unresponsive to antibiotics, the IgG level should be determined. If this level is <200 mg/dl, as determined by SRID, or if the total gamma globulin is <300 mg/dl as determined by densitometry of SPE, then gamma globulin replacement therapy would be appropriate line of treatment. Gamma globulin replacement therapy may have serious side effects like anaphylaxis, so it should be administered at hospital or nursing home, under strict medical supervision. A variety of commercial gamma globulin preparations are available for intramuscular injections. The dosage must be adjusted to ensure minimum of 0.1 g/kg of IgG per month or 0.025 g/kg per week. The dosages are determined as milliliter per kilogram dose as per instructions on the vial. A variety of side effects are anticipated in about 20% of patients getting regular gamma globulin replacement therapy. There may be anxiety, facial swelling, flushing faintness, hypotension and dyspnea. In cases of secondary hypogammaglobulinemia, at first the underlying disease responsible for causing hypogammaglobulinemia needs to be treated. Gamma globulin replacement therapy is administered in very severe cases of secondary hypogammaglobulinemia. IgG levels in the sera are determined at regular intervals to monitor the clinical course and therapeutic response of patients with immunoglobulin deficiency disorders.
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