"Effect of the Novel Influenza A (H1N1) Virus in the Human Immune System"
The effect of H1N1 on the human immune system is a hot topic of research.  In this study, H1N1 infected patients had peripheral blood drawn to determine their absolute counts of monocytes and lymphocytes.  Peripheral blood mononuclear cells (PBMCs) were then isolated and stimulated with various bacteria and protein antigens.  An increase in monocytes was noted in patients infected with H1N1.  Concentrations of tumor necrosis factor-alpha, interleukin (IL)-1beta, IL-6, IL-18, interferon (FN)-alpha and of IFN-gamma were also calculated.  The researchers then added phytohemagglutin and heat-killed Streptococcus pneumoniae to the peripheral blood of H1N1 infected patients and found they had a defective cytokine response.  Patients infected with H1N1 had a decrease in the number of CD4-lymphocytes and B-lymphocytes and an increase in T-regulatory lymphocytes.  The authors concluded H1N1 virus causes impairment of the innate immune responses and defective cytokine response to S.pneumoniae, predisposing these patients to pneumococcal infections.

Giamarellos-Bourboulis EJ, Raftogiannis M, Antonopoulou A, Baziaka F, Koutoukas P, Savva A, Kanni T, Georgitsi M, Pistiki A, Tsaganos T, Pelekanos N, Athanassia S, Galani L, Giannitsioti E, Kavatha D, Kontopidou F, Mouktaroudi M, Poulakou G, Sakka V, Panagopoulos P, Papadopoulos A, Kanellakopoulou K, Giamarellou H. "Effect of the novel influenza A (H1N1) virus in the human immune system" PLoS One. 2009 Dec 23;4(12):e8393
http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0008393