Immunocompetent individuals produce both IgM and IgG antibodies in response to most pathogens. In most cases, IgM is produced by a patient after the first expo sure to a pathogen and is no longer detectable within a relatively short period. For serologic diagnostic purposes, it is important to note that IgM is unable to cross the placenta. Therefore, any IgM detected in the serum of a newborn must have been produced by the infant and indicates an infection in utero. The larger number of binding sites on IgM molecules provides for more rapid clearance of the offending pathogen, even though each individual antigen binding site may not be the most efficient for binding to the antigen. Over time, the cells producing IgM switch to production of IgG. IgG is the highest circulating antibody in the human body.

IgG is often more specific for the antigen (i.e., it has higher avidity). IgG has two antigen binding sites, but it can also bind complement. Complement is a complex series of serum proteins that is involved in modulating several functions of the immune system, including cytotoxic cell death, chemotaxis, and opsonization. When IgG is bound to an antigen, the base of the molecule (Fc portion) is exposed in the environment. Structures on this Fc portion attract and bind the cell membranes of phagocytes, increasing the chances of engulfment and destruction of the pathogen by the host cells. A second exposure to the same pathogen induces a faster and greater IgG response and a much lesser IgM response. Several B lymphocytes retain memory of the pathogen, allowing a more rapid response and a higher level of antibody production than the primary exposure or response. This enhanced response is called the anamnestic response. B-cell memory is not perfect. Occasional clones of memory cells can be stimulated through inter action with an antigen that is similar but not identical to the original antigen. Therefore, the anamnestic response may be polyclonal and nonspecific. For example, reinfection with cytomegalovirus may stimulate memory B cells to produce antibody against Epstein-Barr virus (another herpes family virus), which the host encountered previously, in addition to antibody against cytomegalovirus. The relative humoral responses are diagrammatically represented in Figure 1.

Fig1. Relative humoral response to antigen stimulation over  time. 

اخر الاخبار

اخبار العتبة العباسية المقدسة

الهيأة العليا وجمعية العميد تعقدان اجتماعا لمناقشة آليات التعاون العلمي المشترك

لتقديم الدعم النفسي والمعنوي قسم الشؤون الطبية يزور أطفال مرضى السرطان في مستشفى الإمام الحسن (عليه السلام)

قسم الشؤون الفكرية يهدي إصداراته الحديثة إلى مكاتب المراجع وعدد من المؤسسات في بابل

عبر مركز الكفيل للصحة والسلامة.. قسم الشؤون الطبية يستأنف ورش الإسعافات الأوّلية للمنتسبين

المزيد

الآخبار الصحية

سرّ بسيط لصحة القلب.. أطعمة تخفض الكوليسترول خلال أسابيع

سبب خفي لإعتام عدسة العين ؟

عوامل خفية تسرّع شيخوخة الدماغ

أسباب الرغبة الشديدة في تناول الحلويات والأطعمة النشوية

المزيد

الآخبار التكنلوجية

كندا تصنع كاسحة جليد من جيل جديد

رواد "أرتيميس 2" يكشفون تفاصيل حياتهم في الفضاء

حفريات صينية تكشف كائنات بحرية عاشت قبل 546 مليون عام

روسيا تطلق صاروخ "سويوز-2.1 إيه" من قاعدة بليسيتسك الفضائية

المزيد

مواضيع ذات صلة

Interpretation of Serologic Tests

Enzyme Immunoassays

Immunofluorescent assays

Particle Agglutination

Precipitation Tests

Production of Antibodies for use in Laboratory Testing

Investigation of Strain Relatedness/Pulsed-Field Gel Electrophoresis

Detection of Antimicrobial Resistance

The Light Microscope

Identification of Microorganisms Grown in Culture

Direct Detection of Microorganisms

Laboratory Manifestations of Iron Overload