2002 ANNUAL SCIENTIFIC MEETING 91 interact with counter receptors expressed prominently in both normal and inflamed skin. CLA, or cutaneous lymphocyte antigen, is a glycoprotein expressed predominantly on skin homing T cells. Along with chemokine receptors CCR4 and CCR10, CLA initiates the process of T cell extravasation specifically in skin. Interestingly, CLA is expressed during the expansion and differentiation of a recently activated naive T cell in a skin draining lymph node. There is something unique about the microenvironment of a skin draining lymph node because CLA is not expressed by T cells that are first activated in other anatomic lymph node microenvironments (e.g., GI tract, lung). Skin homing memory and effector T cells use CLA to "tether", or bind under flow conditions, to E and P selectin expressed on skin post capillary venules. Again using CLA-selectin interactions, the T cells rolls along the surface of the vessel, exposing its cell surface receptors to ligands expressed on the endothelial wall. Chemokines bound to the wall of the vessel activate the T cell through chemokines receptors, leading to integ-rin activation and firm adhesion between LFA-1 on the T cell and ICAM-1 on the endothelium. This is followed by flattening of the T cell and transendothelial mi•ation through the vessel wall into the dermis. In this location, the T cell can respond to chemotactic gradients. This T cell can also recognize antigen presented to it by dendritic cells in the dermis. Effector T cells produce cytokines when they are activated, and these fall into two general categories. Type I cytokines include •N7 and TNFot, and induce inflammation. Type 2 cytokines include IL-4, IL-5, and IL-13--these cytokines promote allergic responses, characterized by eosinophil and mast cell activation. In both cases, these T cell cytokines are designed to amplify the type of inflammatory response best designed to eradicate the invading pathogen. Most of the time, this elegant system works very well. T cell mediated inflammatory skin diseases occur when the control of this system breaks down. For example, in allergic contact dermatitis, the immune system inappropriately recognizes innocuous chemicals as pathogens, and a population oft cells specific for these chemicals or their modifications is generated. In atopic dermatitis, innocuous environmental antigens, such as those derived from house dust mite, provoke a hyperresponsive skin homing T cell response, here dominated by type 2 cytokine production. In psoriasis, it is thought that the immune system has generated a robust response to an autoantigen in skin in this case, type I cytokines dominate. Cutaneous T Cell Lymphoma is a malignancy of the skin homing memory T cell. In all cases, successful therapies target, directly or indirectly, the skin homing effector and memory T cell. In the future, this research will guide a variety of endeavors that have general biomedical importance. Understanding organ specific T cell t-•, 'uing is critical for making effective cancer vaccines. The ability to generate tumor specific T cells in vitro that can also home appropriately in vivo would change our ability to treat many cancers. T cell trafficking is central not only to cutaneous immunity, but to the success of the human immune response in general.

92 JOURNAL OF COSMETIC SCIENCE WHO SAID SENSORY MEASUREMENT WAS SIMPLE. 9 Michael O'Mahony, Ph.D Department of Food Science and Technology, University of California, Davis, CA 95616 maomaho n y @ uc da v is. e du This talk will demonstrate some of the tricks that the senses might play on unsuspecting persons required to make judgements about the sensations they are experiencing. It will also examine the ways in which people can make mistakes in reporting what they think they are perceiving. Marketing, advertising and packaging are vital for the sale of cosmetics, personal and household products. Yet, there is a further important aspect: the sensory properties. These are the responsibility of the manufacturer and this means that the manufacturer must be able to measure them. Such measurement is necessary for the development of new products, for the measurement of consumer concepts, for quality control, ingredient specification, storage studies, product optimization etc. Although a company will have laboratories full of instrumentation for making such measurements, it tums out that the human senses are often more sensitive to variations in sensory characteristics than many laboratory instruments. So it is necessary to use the human senses as measuring instruments. The problem with humans is that the information processor for their senses is the brain and this was not designed or programmed to mn instrumentation. It was programmed to be the information processor for cavemen and cavewomen. It has the unfortunate habit of enhancing the perceptions that would be useful to a caveman or cavewoman but which can seriously interfere with sensory testing. So, to use the human senses effectively, we have to understand the workings of the nervous system and brain. Then we can avoid the biases that it will introduce into our perceptions and so enable us to make accurate assessments of the sensory properties of the products we are testing. The same argument applies to consumer product testing and marketing measures, as well as more medically related research. There are something like a trillion connections in the brain which makes it the most powerful computer on the planet. Yet, despite this, it cannot process into consciousness all the sensory information that reaches it from the body. It is basically overloaded with information. So it has a set of strategies for avoiding 'information overload'. The first strategy is simple. The brain does not arrange that you pay attention to all the input from the senses. Humans tend to focus on only a small part of the information arriving at its 'door': visual and sound input. Animals tend to focus on smell. The second strategy has been given the technical name of 'sensory adaptation'. This refers to the mechanism in the brain that allows it to disregard redundant information. If a stimulus is completely unchanging, the brain does not want to pay attention to the senses as they keep repeating the same message over and over again. It is too busy processing other information for it to be bothered with the same redundant message being repeated again and again. So it simply turns down the volume switch on those repeated messages for the sensation to vanish or at least be greatly reduced. But if there is even a slight change in that message, the sensation reappears loud and strong. This is a common everyday experience. Imagine that you walk into a room and you immediately notice that there is a slight smell there. As you walk around the room your nose will be sniffing the same concentration of volatile chemicals because they have reached some equilibrium concentration throughout the room. So the stimulation at the nose is constant. The input reaching the brain is constant. So the brain, which is too busy processing other information to bother with repeated stimulation, simply tums down the volume switch and the smell slowly vanishes. The smell system has been desensitized or adapted to that particular odor. Yet walk out of the room and come back in again and the smell will reappear. There will be a change in the volatile chemicals surrounding the nose as you leave and re-enter the room, so the brain tums up the volume switch once more and the smell re-appears.. It is said that you can only smell a rose once. This is not completely true but the smell of a rose is reduced as you repeatedly sniff its aroma. Everyone will be desensitized to perfumes or colognes with repeated sniffing. This can be inconvenient for any form of sensory assessment. Thus, the sensory analyst must work out ways of getting round this problem my making sure that the assessement of a scent is completed rapidly before it vanishes. It is also important that the nose is cleared by removing it from the area, before assessing the next scent, so as to defeat this desensitization effect. This desensitization does not only apply to smell it applies to all the senses, even vision.