Presenting the Immune System as a Model for Design

Shari L. Cheves
Microbiology 300 IC
Spring 1994


"Design by symmetry works by juxtaposing concepts that are similar at a very deep level - the concepts are symmetric in terms of some deep structure or underlying process." (Laurel, p. 12) In Erickson's view, design symmetry follows three characteristics in that it: 1) produces a conceptual framework, 2) is suited for cross-disciplinary work and 3) once explored, can be extended in many directions. (Laurel, p. 12) The immune system, as a product of networked components and a process of maintenance and surveillance, can be closely compared in "symmetry" with visionary or successfully implemented design principles. The following study will present specific parallels to build a framework of the immune system model before exploring direct and indirect applications to design.


Building the model



Form

The immune system performs a number of functions critical to maintaining homeostasis of the body. All components involved in this delicate process present basic interrelationships of form and function. Proteins, for example, contain interacting amino acids which help coil the protein into a unique three-dimensional structure. This specific structure can affect such critical immune activity as cell circulation, enzymatic reactions, and antibody binding. The hemoglobin protein of the red blood cell establishes the "lozenge" shape which maneuvers easily throughout the vessels. Sickle hemoglobin is a protein which, when replacing normal hemoglobin, precipitates in the cell causing it to form a sickle shape. This new shape "cannot carry oxygen, cannot circulate well and is easily destroyed." (Itatani, ch. 3, p.4) Platelets which reside in blood plasma also have the ability to change shape when clotting is necessary. "In order to perform this job, the platelets adhere, and change shape from smooth plate-like discs to spiny, star-shaped bodies" (Itatani, ch. 8, p.7) which better interlock to plug the gaps and chemically activate other healing factors. In the design of transportation vehicles, this issue of form and "aerodynamics" has become a popular example of physical translation of function. From submarines to airplanes to racecars, design has emphasized less resistance through smooth, accelerating curved surfaces. Considering the malliability of shape is yet another possible design objective, approached in products like the Space Shuttle's rocket-glider conversion feature.

Enzymes are also proteins which rely upon unique shape to function; an enzyme and a substrate act as a "lock and key," chemically reacting upon complementary contact. In the design of products with locking or additive components, precise fit of form is often imperative for function as well as durability and safety. Security locks and clasps are obvious examples - much electronic equipment also involves insertion of media like cassettes, compact discs and computer floppy disks. The compartments designed to accept these materials must accurately consider form and implementation of form to work effectively.

Antibodies are composed of unique shapes and compositions optimized for binding to foreign organisms - antigens - and facilitating cell lysis and ultimately bacterial destruction. Antibodies, generally termed "immunoglobulins," are proteins chemically linked in the shape of a "Y." The arms bind to the bacteria, leaving the stem exposed for easy complement binding and consequent lysis. Variable regions located on the ends of the arms also contain "variable sequence of amino acids to assure specific antibody binding to antigen." (Itatani, ch. 6, p.7) Similarly, the design of handles or receivers on products can drastically affect the nature of interaction, i.e. forks can differ in effectiveness of both food retrieval and user handling. Fork spears can be too rigid or too flexible to respond appropriately to a specific food. Fork handles can also be too long or thin for a particular individual to grasp. In applying the immune system model, this product might have "variable regions" in these areas in order to best perform diverse tasks.

Flexibility and movement are also significant to immunoglobulin function. "The functional sites are located in different parts of the Ig molecule, and flexibility seems to be a crucial factor for otimal binding to several different ligands, often simultaneously. The functional importance of flexibility is obvious after comparison with findings that hinge-deleted nonflexible Ig's lack major effector functions." (Dixon, p. 33) Biochemical hinges serve to increase execution of function, just as use of flexible materials and forms in design can facilitate tasks and improve product performance.

Composition

In addition to form, the complex composition of immune elements contributes to successful immune response and bodily function. Cell membranes, for example, are made of an array of phospholipids, glycolipids, and glycoproteins which chemically arrange themselves to form layers. The glycoproteins and glycolipids, with unique shapes (and therefore different functions) protrude out of the outer membrane layer, acting as "antennae for receiving chemical messages. They are also recognition markers that establish cell identity and allow cells to recognize each other." (Itatani, ch. 3, p. 6) This significant feature is the basis of self and non-self cell recognition in the immune system. T-lymphocytes can distinguish between "self" antigen normally present in the body and "non-self," harmful antigens. Fortunately, the education of these T-cells occurs under close supervision in the thymus where misprogrammed T-cells are destroyed. T-cells mature into a variety of types based on function and surface cluster designations (CD). These CD markers facilitate binding, cell interaction, cell communication and other specific functions.

In design, "interface" parallels the cell membrane as a "contact surface" of a product. "It reflects the physical properties of the interactors, the functions to be performed , and the balance of power and control." (Laurel, p. xii) This relatively new design consideration can be further expanded to become a more functional unit of the product, just as the CD markers, glycoproteins and glycolipids do more than identify and label. New technology introduces "the possibility of integrating properties of sensitivity and information capacity into final composite material." (Manzini, p. 29) Systems formerly composed of distinct parts can now be merged into the objects "material" - possibly a skin or membrane. This two-dimensionality can be applied to a multitude of purposes: "a tennis court that can feel and indicate whether the ball went out of bounds; a plate that can reconstruct the shape of an object that was set on it; the surface of an instrument for orthopedic exams that can produce a diagram of the pressure exerted by the patient's foot." (Manzini, p. 203) These visionary designs identify, communicate, and interpret in the same sensitive fashion as cell components function within the immune system.

Size and Activity

Immunoglobulin size and circulation also facilitate function and maintenance within the immune system. Surveillance of immune conditions is accomplished by the circulation of lymphocytes "reduced and simplified to the smallest size possible for ease in transport around the body." (Itatani, ch. 4, p.7) They don't carry much cytoplasm, as their primary function in this resting state is scouting and recognition of foreign antigens. Lymphocytes can circulate in and out of tissues via the lymphatic vessels - a network of open-ended transport vessels. Lymph nodes along these vessels perform much of the immune filtering and communication in well-managed, monitored organs. In the design of complex systems, this "decentralization" of activity may suggest manageablility and efficiency. Electrical power, for instance, is distributed through capacitors which "store" power until allocation is necessary. Computer interface designers often confront problems in simplifying networks of circulating information similar to the complex paths and processes of the lymph system. However, ". . . information to be managed is more complex and theoretical, and it is hence more difficult to interact with a range of options that appear as a growing number of signals emitted in a multitude of different codes . . . Any approach to reality that intends to make it understandable must involve the use of a filter . . ." (Manzini, p. 56) Hence, computer interface designers are now exploring user-defined filters and navigation systems to help users circulate through the information pathways, focusing energies in specific centers of communication exchange. The immune system contains many filters and "network centers," including lymph nodes, spleen and lymphocyte aggregates which can vary in size and activity according to antigen. Studying the variability of these immune components might also help designers better organize paths and create practical filters for the growing amount of information accessible today.

Diversity

The immune system's multitude of diverse elements is yet another critical factor in the primary function of homeostasis. Diversity of red and white blood cells begins with hematopoiesis - the generation of a multi-potential cell type which can differentiate into numerous other functionally specific cells. Many of these cells interact in order to perform other functions; for example, T-helper cells rely on the macrophage's ability to display antigen and MHC II in order to stimulate B-cell production of antibody. "...The lymphocyte populations as a whole have antigen receptors which can specifically recognize any biological molecule . . . The majority of these specificities will never be needed, but it is only by this means that the immune system maintains its full potential to respond." (Owen, p. 1) Other types of T-cell lymphocytes proliferate as chemical messengers are released in these interactions. Antibody diversity also contributes to effective immune response; larger "loaded" IgM antibodies precede smaller, more specific IgG antibodies for a better offensive attack on antigen invaders.

Diversity and differentiation have become evolutionary advantages in the immune system. Macrophages - the primary phagocytosing "digesting" cell - are associated with nutrition in primitive animals. "An important newer role of participation in the immune response has been acquired in advanced invertebrates and vertebrates. Macrophages have been shown to trap, process and store antigens, and are thus a cell type necessary for the induction of an immune response." (Marchalonis, p. 105) Perhaps differentiation of our environment has created a survival advantage for diversity and multiple cell functions. Certainly the DNA molecule allows for these changes in its vast but finite ability to recombine and diversify organic material with a success rate of only "one error in every billion nucleotides copied." (Sagan, Druyan, p. 85)

Diversity is critical in design consideration as the product's ability to recognize and meet the needs of diverse individuals usually contributes to its effectiveness of use and marketablity. Ergonomics is one branch of design that has emerged to recognize the diversity in human form in order to create comfortable environments or products. Diversity is usually accommodated through adjustable components of a design, i.e. changing form, color, light, etc. Differentiation is yet another method of meeting diversity, performed on a small scale through design of modules or customizable parts of products. In the future, modifiable interfaces with base, "multi-potential" units could serve as versatile products capable of adjusting to different tasks and user needs just as immune cells differentiate for a diverse network of functions.

Communication

On the level of form, composition and diversity, communication plays a vital role in successful immune response as well as general homeostasis. Inflammation is one example of this process, enlisting the cooperation and collaboration of numerous chemical agents and lymphocytes to aid in healing. A chain reaction occurs as chemical mediators increase blood flow, vessel permeability, and white blood cell migration (chemotaxis). Cytokinins, some of the chemical messengers expressed in these reactions, trigger pyrogen release which communicates with the brain in controlling temperature. Higher body temperatures therefore encourage metabolism and inhibit bacteria growth. Interleukins, interferons and other cytokinins also interact with the brain to facilitate immune response. (Itatani, ch. 14, p. 3)

A new field of investigation has emerged to study immune system communication with the brain - psychoneuroimmunology. Just as "lymphocytes and macrophages talk to each other via lymphokines and cytokines . . . neurons and immune cells [may] talk to each [other] via shared receptors for these same chemical messengers." (Itatani, ch. 14, p.6) Adaptive responses like fever, loss of appetite and fatigue can also be linked to immune-nervous system communication, further enhanced by the presence of nerve endings in immune organs. Even major and minor life stress have been shown to affect the immune system, deepening the interrelationship of psychological and immunological activity.

These intriguing correlations, though barely explored, illuminate the significance of understanding communication between interrelated systems. In design, one similar relationship being explored regards the study of human factors. Psychological as well as physical effects of design features are analyzed to establish guidelines for more successful "user-friendly" products. Products and systems, regardless of simplicity of form or function, all "communicate" with the user and vice-versa; though this interraction varies in type and intensity, the intent of the product (to perform a specific function) relies upon interaction. For instance, a colored light indicator on a product may indicate an operational problem, heat (temperature), or even simply enabled power. However, the user is expected to relate the light's color to its appropriate definition.

Messages of color are being explored as a medium of communication even in computer interface design: "It seems possible that we could use distinctive colors similarly - colors that appear in certain contexts could aid recognition and recall." (Laurel, p, 274) If the designer can closely control or predict this communication process, a desired response may become more achievable. Methods of enhanced information communication have traditionally involved static graphical display, but new technology has introduced audio and even motion for presenting signals and concepts. (Laurel, p. 153) These new "interface" components further increase the number of psychological response variables, and, like psychoneuroimmunology, must be studied in relation to human behavior in order for design to better meet the needs of individual consumers.

Some of the key functions of the immune system and their relationship to established, emerging, or visionary design principles and products have been presented. Application of immune system components and immunological experimentation methods can now be explored to expose new parallels and possibilities in the design thinking and creating process.


Application to design


Physical application

Direct physical application of the powerful functions resident in the immune system involves the integration of immune components, particularly at the molecular level, in products. This technique is most popular in the drug design industry, where organic molecules and cells found in the immune system are "repurposed" or combined to perform powerful immunoresponsive tasks. For example, "researchers have found that they can inhibit the development of experimental encephalomyelitis in rats by feeding them myelin basic protein before giving them injection of the protein." (Itatani, ch. 13, p. 14) Experimental vaccines for the AIDS virus explore use of the HIV virus coat to induce antibody proliferation. Many of these organic ingredients have been extracted from the immune system's vast pool of resources in order to make therapeutic progress.

Yet these versatile elements have been exploring even more uncharted territory in the new field of nanotechnology. With the speed and accuracy of molecular duplication and the spontaneous complex shape formation of organic substances, "self-assembly" of thousands of molecules might occur; "organic" robots or self-regulating computers might result from laboratory synthesis of these materials. (Langreth, p.75) Computer scientists may be the first practical users of nanotechnology, as atomic switches have already been constructed and progress is being made in developing memory devices, transistors, and other electrical components. Drexler, however, proposes a broader future for nanotechnology as it diffuses into other disciplines; "microbe-size machines will soon plunge into the body to repair clogged arteries, uncover minerals deep beneath the earth, and construct skyscrapers from the ground up." (Langreth, p. 72) Viruses, environmental pollutants, and other microscopic targets may be detectable and isolated with atomic or protein driven structures. Specific examples of component nanotechnological applications as described by research Eric Drexler are listed below. Aside from sheer physical advantages, nanotechnology may also alleviate many global complications posed by current design and manufacturing processes - namely limited natural resources and environmental pollution.

Device Function Molecular example
Struts, beams casings Transmit force; hold positions Microtubles, cellulose
Cables Transmit tension Collagen
Fasteners, glue Connect parts Intermolecular foces
Solenoids, actuators Move things Conformation-changing proteins, actin/myosin
Motors Turn shafts Flagellar motor
Drive shafts Transmit torque Bacterial flagella
Bearings Support moving parts Sigma bonds
Containers Hold fluids Vesicles
Pumps Move fluids Flagella, membrane proteins
Conveyor belts Move components RNA moved by fixed ribosome
Clamps Hold workpieces Enzymatic binding sites
Tools Modify workpieces Metallic complexes, functional groups
Productions lines Construct devices Enzyme systems, ribosomes
Numerical control systems Store and read programs Genetic system
Table 15.1 (Drexler, p. 446)


Methodology

A more indirect approach to using the immune system model applies contemporary immunological experimentation methods to design methodology. One primary example is structure-based design - "an innovative approach to developing drugs" (Bugg, Carson, Montgomery, p. 92) - which diverges from the standard tactics of "trial-and-error" by studying the nature of the problems in the body. Rather than "discovering" a drug to remedy a disease, structure-based researchers begin the design process by solving "the three-dimensional structure of a substance known to participate some disorder. Then [they] build a chemical that precisely fits the target and alters its activity." (Bugg, Carson, Montgomery, p. 92) This honing method yields benefits of time and economy as well as a clearer understanding of ambiguous processes. In one example, structure-based design revealed an enzyme shape change between molecule bindings - a consideration of key importance in designing the appropriate drug to inhibit the enzyme.

Design methodology in other fields might also exploit this direct exploratory approach in order to understand a proposed problem and solve it within the time and economic constraints of modern demands. Successful exploration requires "the ability of designers to overcome the cultural inertia that can prevent them from 'seeing' the new, and their ability to direct design processes that can accommodate the new. All of this . . . depends in turn on the preparation of an underlying connective tissue made up of an awareness of the non-linear nature of the design process . . ." (Manzini, p. 61) Immunological researchers methodically search to discover the new, whereas designers often hope (indefinitely) for an epiphany or visual inspiration for design solutions - a much less reliable, uncompromising method of problem-solving. Even in the event of accidental discovery, "creativity is . . . exhibited . . . when the individual realizes that the accident could be plumbed further." (Weisburg, p. 243) This is exemplified in immunology history when Alexander Fleming discovered penicillin from a mold spore blowing through his laboratory window. Likewise, Louis Pasteur discovered the principle of the vaccine when he accidently inoculated specimens with aged, attenuated bacterial culture - only to find that they did not later react to fresh bacterial culture. By applying these principles to other experiments, Fleming and Pasteur expanded the impact and success of their research. An understanding of the relational thinking process, recognition of design potential, and conscious exploration of new perspectives can similarly help structure and unfold the creative success of the designer.

Another method of experimentation in wide use by immunologists and researchers incorporates the evolutionary process; time and natural reagents contribute to the formation or identity of a desired product. Monoclonal antibody technology is one prominent example, cloning and fusing B-cells with cancer cells in order to create a "hybridoma" which performs the B-cell's specific antibody production at an uncontrollable "cancerous" rate. Laboratory-developed monoclonal antibodies can then be injected to help identify specific cell types and even attack cancer cells. This clever exploitation of natural immune function may directly and indirectly contribute to design. Nanotechnologists, for instance, need "developing proteins that bind to the correct surface site" (Drexler, p. 448) in order to assemble organic blocks and structures. Monoclonal antibody technology promises this control of recognition and specificity. Evolutionary processes can be indirectly applied to the industrial design field, where the idea of repurposing natural and/or original material has been somewhat realized in the proliferation of recyclable products. However, the use of natural (biological) processes is yet unexplored in most design solutions. Product aging, for example, is routinely considered in the objective of producing an unchanging, eternally "new" product. Time prohibits this, of course, and most products must be destroyed or refurbished within a matter of months or years. An alternative design solution to this inevitable reaction might use natural or even synthetic materials, microscopic or macroscopic, to identify changes in material composition and form. Corresponding "designed" reactions could then take place, just as monoclonal antibodies can be produced to identify and elicit immune response. Using this and other "sensitive" evolutionary methods, products and systems can become aware and reactive to environmental changes as well as human interactions.

In summary

As illustrated, the immune system can be a dynamic, multi-faceted model for design in many fields. Its specific structures and networked performance demonstrates a collaborative efficiency surpassing any man-made system. In attempt to understand and even control this complex system, researchers have also presented new, innovative techniques in problem-solving. Though we cannot yet harness the physical power of the immune system in other disciplines, we can construct new parallels to build the bridges between our natural and designed environments.

Those who are enamored of practice without science are like a pilot who goes into a ship without a rudder or compass and never has any certainty where he is going. Practice should always be based upon a sound knowledge of theory.
- Leonardo da Vinci




Bibliography

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