Sub Populations of Immune Cells in Influenza A and B Patients

Background:

In late March and early April 2009 an outbreak of a novel influenza virus designated A/H1N1 influenza (popularly known as swine flu) was reported in Mexico, with subsequent cases observed in many countries, leading to the declaration by the World Health Organization of a worldwide pandemic.

The first case of influenza A/H1N1 in Israel was diagnosed at the end of April 2009 at Laniado Hospital in a young man returning from Mexico.

Influenza A/H1N1 (Swine flu) carries a relatively high morbidity, particularly in young patients. Early identification would enable prompt initiation of therapy, thereby improving outcomes.

In 2009, during the H1N1 pandemic in Israel, a research was conducted in our department of pediatrics. The researchers Sharon et al. (1) have compared a group of 53 children infected with Influenza A H1N1, with a group of 53 children that presented with flu symptoms but were found negative for the virus. This comparison demonstrated a significant reduction in lymphocyte count during the acute phase of the disease (days 1-3) with resolution on day 7 (6-9) as well as reduction in the neutrophil count on day 5 from the onset of high fever with subsequent resolution 2-4 days later (days 7-10). This phenomenon was not observed in the patients that were not infected with the H1N1 virus. Similar results were reported by Cao and co-authors (2) that observed it in both pediatric and adult patients. Lewis at al suggested that the lymphopenia is mainly due to reduction in T cells and to a lesser extent in B cells (3). The lymphopenia typical of influenza A H3N3 during acute illness was shown to be due to a reduction in both T and B cells without alteration in the CD4:CD8 ratio. This is in contrast to the findings of Cao et al. (2) who noted an abnormal CD4:CD8 ratio in half of those who were positive for A H1N1. One of the possible explanations as proposed by Nichols and Collaborators (4) is that early lymphopenia and the later neutropenia in the influenza infected patients may represent migration of these cells from the circulation to the infected respiratory tract as a consequence of infection. Goals of our research To quantify the B, T and NK populations of lymphocytes during different stages of the disease caused by Infuenza A H1N1.