Until recently, B lymphocytes have not been thought to inhabit non-mucosal human skin. They have traditionally been viewed as major elements of the immune system strictly confined to blood and bone marrow. This study reports the novel finding of B cell infiltrates in herpes simplex virus 2 (HSV-2) skin lesion biopsies. Motivated by an interest in the underlying immune mechanisms responsible for the wide spectrum of disease seen in those suffering with reoccurring HSV-2 lesions, I examined the immune microenvironment of tissue biopsies from study participants with active herpes lesions and a history of frequent outbreaks. In order to study the local immune response of an HSV-2 reactivation episode, I analyzed skin sections of herpes lesions using fluorescence in situ hybridization (FISH) to demonstrate the cell marker and immunoglobulin expression profiles of skin-resident immune cells present at the time of herpes outbreaks. Through the use of FISH and advanced deconvolution microscopy, I proved that B cells of the human immune system can home directly to upper layers of the skin to fight HSV-2 reactivation. My work reveals the presence of immune cell populations in HSV-2 lesions showing RNA expression for CD20, CD138, CD4, IgG, IgM, and IgA. This study demonstrates that antibody-producing cells are recruited to sites of HSV-2 reactivation, secrete a variety of antibodies at the site of infection, and appear to interact closely with CD4+ T cells directly in skin. B cells may play a crucial role in the immune response required to effectively control HSV-2 reactivation, which has been underappreciated until now. My work suggests that individuals with immune systems that are less efficient at recruiting B cells to the upper layers of the skin to control HSV-2 infection may explain why some individuals suffer more severe manifestations of the disease than others throughout their lives.

Fear is an emotion that is triggered when an organism encounters danger or threat. Once fear is triggered, the nervous system induces many physical changes, and the brain responds accordingly to elicit defensive or fleeing behavior. Such fear responses are known to involve a critical brain region called the amygdala. One of the ways in which the amygdala mediates fear response is by secreting a neuropeptide called corticotropin-releasing factor (CRF). Our lab has previously found that CRF-expressing neurons in the central nucleus of the amygdala (CeA-CRF neurons) facilitate the acquisition of discriminatory fear responses and prevent fear extinction. In contrast, others have reported that activation of CeA-CRF neurons is reinforcing. To resolve these contradictory findings, we investigated the functional roles of CeA-CRF neurons in naïve and fear-conditioned mice. We hypothesized that activation of CeA-CRF neurons in a neutral context may produce reinforcing effects by signaling a type of salience. However, following a fearful experience these neurons may signal the aversive nature of this experience. To stimulate CeA-CRF neurons selectively, we used optogenetics, in which light-sensitive ion channel-expressing neurons are stimulated using light, and animals underwent several behavioral tasks including operant conditioning for lever pressing, real time place preference task, and elevated plus maze test. Based on the animals’ emotional context (naïve or fear-conditioned), we examined how stimulation of CeA-CRF neurons affected the animals’ behavioral performances. Our results showed that stimulating CeA-CRF in naïve mice produced no effects. However, if the animal’s first experience in a context was appetitive, then stimulating in this context is reinforcing. Similarly, if an animal’s experience is aversive, then stimulating these neurons perpetuates fear and anxiety behaviors. These results suggest that CeA-CRF neurons signal context-dependent behavioral state effects that may be important for engaging appropriate actions in specific contexts.