Changes in memory and naive CD4+ lymphocytes in lymph nodes and spleen after thermal injury.

T cells expressing CD4 can be further subdivided by their expression of CD45R. In humans, CD45RO+ cells function as memory T cells, and CD4+CD45RA+ function as naive T cells, i.e., cells that have never previously encountered antigen. In the rat, similar functional division of CD4 cells can be made with antibody OX-22 (anti-CD45RC) with CD4+CD45RC- and CD4+CD45RC+ identifying the memory and naive phenotypes respectively. With use of the rat model, we studied the effect of burn injury on CD4 cell subpopulations and memory and naive T cells in lymph nodes draining the burn wound (NDB) and spleen. In the NDB we found that numbers of memory and naive CD4 cells increased significantly as a function of time after burn injury, and that this increase was greater for naive cells (5.7-fold) than for memory cells (4.1-fold). However, in the spleen, we found memory T-cell numbers decreased significantly on postburn days 12 and 18, whereas naive CD4 cells in the spleen manifested no changes at any time after burn. These results may be explained by the different trafficking patterns of memory and naive cells. Based on the cell surface marker, L-selectin, naive cells preferentially migrate into the NDB where they undergo differentiation into memory cells. Memory cells selectively migrate into inflamed burned tissue, which may account for their lesser-fold increase in NDB when compared to naive cells, and their decreased numbers in the spleen after burn injury.

Hepatitis B immunization in adolescents.

This article reviews the epidemiology of hepatitis B in the United States, previous vaccination strategy, and reasons for its failure and issues leading to the recommendation to vaccinate all adolescents. A review of specific hepatitis B virus risk behaviors of adolescents and barriers to vaccinating adolescents is covered. Strategies that favor successful completion of the immunization series are also examined. Hepatitis B infection is an important public health concern for adolescents. The previous vaccine strategy to immunize only individuals though to be at high risk was unsuccessful, especially because providers of care could not identify these individuals. Furthermore, many individuals thought not to be at high risk for infection were exposed through contacts which could not be identified. Challenges to immunization of adolescents include logistical issues, patient education, cost of the vaccine, and patient compliance. Several of these issues can be addressed by a school-based hepatitis B immunization program. The body of evidence and national policy is rapidly changing to support the recommendation that all adolescents receive the hepatitis B immunization series. The series would be most effective if administered during the middle-school years. A universal adolescent hepatitis B vaccination program would result in the most immediate health benefits and acceleration toward the eradication of hepatitis B in the United States.