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TreatmentUpdate 173Volume 21 Issue 4 2009 May/June II CANCER: B. Predicting who is at high risk for lymphomaHIV infection weakens the immune system and increases the risk for life-threatening infections. HIV positive people are also at increased risk for the development of tumours. This risk arises because of a combination of weakened immunity and co-infection with a number of sexually transmitted cancer-causing viruses, as follows:
Now that highly active antiretroviral therapy (HAART) is widely available in high-income countries, this therapy has helped to greatly reduce deaths from life-threatening infections. HAART works by suppressing production of HIV. In turn, this allows the immune system to begin to repair itself. Regrettably, HAART does not cure HIV infection and the immune system is only partially repaired. This means that a degree of immune deficiency continues. About the immune systemBefore delving into lymphoma, here is some important information about the immune system. This vast system consists of a network of vessels called the lymphatic system, which connects important organs such as the thymus and spleen as well lymph nodes and patches of lymph tissue throughout the body. Key cells that are part of the immune system and relevant to the formation of lymphoma are T-cells and B-cells. More than an immune deficiencyInitial theories about how HIV damages the immune system suggested that immunity was suppressed. This made sense because the infections seen in AIDS were those associated with immune suppression. But a closer and more sophisticated look at the immune systems of people with HIV/AIDS suggests a complex picture with part of the immune system—particularly B-cells—being overactive. B-cells produce antibodies that can help control some infections. Over-stimulated B-cells—as seen in HIV infection—produce excessive levels of antibodies. This over-stimulation occurs because of HIV. And over-stimulation combined with viral co-infections such as EBV can lead to trouble. EBV can transform B-cells, channeling their growth away from a healthy member of the immune system to a cancerous cell that later forms a tumour. These types of cancers are called lymphomas. Although lymphomas can arise from both T-cells and B-cells in HIV/AIDS, malfunctioning B-cells are the main source of lymphoma. One way to reduce the risk of lymphoma is to use HAART and raise CD4+ counts. However, for reasons that are not clear, not all HIV positive people have high CD4+ counts as a result of using HAART, and the risk of cancer remains. Researchers at the U.S. National Institutes of Health (NIH) have been monitoring the types of tests being explored in other cancers to assess who will develop, recover and relapse from cancers. One test, called FreeLite, assesses levels of fragments of antibodies in the blood. A recent study suggests that monitoring levels of antibody fragments may be useful in predicting the onset of AIDS-related lymphoma. About antibodiesUnder the microscope, antibodies look a bit like the letter Y. They are made up of two basic parts, the bottom part of the Y is called the heavy chain and the two upper parts of the Y are called light chains. To make antibodies, B-cells make both heavy and light chains and put them together. Sometimes B-cells make too many light chains and the excess is released into the blood. When light chains are unattached to heavy chains and are released into the blood, researchers refer to these light chains as free light chains. Cancer studies are underway in HIV negative people to assess changes in levels of free light chains and the development of cancer. Study detailsResearchers at the NIH reviewed health information from three groups of people as follows:
In these three groups there were a total of 66 HIV positive people who had confirmed diagnoses of non-Hodgkin’s lymphoma (NHL). About 60% of lymphoma cases occurred before 1997. Researchers matched each of the 66 people with up to four other people—of the same ethno-racial group, age and CD4+ count—from the three cohorts that did not have NHL. The study team obtained stored blood samples from the three groups and performed various laboratory tests, including assessing levels of free light chains. ResultsResearchers found that between two and five years before the development of lymphoma, the 66 lymphoma patients had higher-than-normal levels of free light chains. Their levels of free light chains were higher than in HIV negative people and HIV positive people without lymphoma. The NIH team concluded that assessments of free light chains were sensitive and could detect dysfunction in B-cells before lymphoma developed. They speculated that perhaps free light chain assessment could be used to monitor recovery and relapse in HIV-related lymphoma. The findings from the NIH study are encouraging but a prospective study to explore assessments of free light chains in the present era is needed to confirm and explore this idea for HIV-related lymphoma and perhaps other cancers. REFERENCES:
Created on: 2009 June 9 Author: Hosein SR |
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Decisions about particular medical treatments should always be made in consultation with a qualified medical practitioner who is knowledgeable about HIV-related illness and the treatments in question. MORE | |