Immunoglobulins and related molecules.

Immunoglobulins and related molecules give humans immunity from infection by microbial organisms. How's that for a circular statement? Circles are not irrelevant to considerations of the subject of immunology. In fact if the beginning were a good place to start, circles would be a good beginning.

Most people think of lines when they think of antibodies. Some people think of chains. Some people think of combinations of all three; circles, lines, and chains. Some think of blobs and some think of globs. Some people draw a blank. That's really sad because antibodies are so interesting. Why? Because immunoglobulins and related molecules give humans immunity from infection by microbial organisms. Not only that but the way in which so many tiny atoms form themselves into huge and regular formations to carry out a multitude of functions which defy the Law of Entropy zillions and skillions of times is truly awe inspiring.

Let's consider some circles.

First scientists have guessed what may have been going on at the molecular level for any given group of molecules and their associated functions. When everybody is sure about the shape of a molecule and/or its function, drawings are used to help in the conceptualization process. In the decades since the discoveries of the structures and functions of immunoglobulins, several types of stylized pictographic conventions have been in use for the depiction of antibodies. They are vastly simplified and schematic in comparison to actual three dimensional structures of the molecules they represent. The various conventions are used to emphasize selected aspects of these complex molecules. The simplest drawings of immunoglobulins are not globby at all; they are just straight lines. This helps to emphasize the categorical similarities and differences of the classes and isotypes of light and heavy protein chains. The most familiar convention is the presentation of a generic antibody molecule as a Y, or a Y with two double arms. Although somewhat stiff and unrealistic this convention is useful for depicting the linear relationship of the constituent parts, particularly the sequences of amino acid residues. Sulfur containing amino acids are important determinants of the structural conformations of immunoglobulins. Consequently there are several conventions for the representation of disulfide bonds within and between protein chains; some have two S's, some are circles, some curved lines, some rectangular, some just a single straight line. An early stylistic convention for the representation of antibodies is a combination of lines and loops in a doubled-arm Y shape such that the size and proportion of the disulfide bonds are relatively small but their effect is more easily conceptualized. Disulfide bonds sometimes pinch and constrain a chain of amino acids into a rounded globular shape. Sometimes they join chains. And sometimes they allow degrees of freedom of conformational flexibility such that in certain regions they contribute to both rotational movement and lateral deformations which have been described as wagging, waving and flapping. Such conformational flexibility is necessary for increasing the probability of obtaining secure bonding with antigenic determinants. Protein data bank files are complex and require careful manipulation. While they are profoundly interesting in themselves, pdb files greatly enhance appreciation of immunoglobulin structure. For example tip of the N-terminal end of the Y is considered, more often than not, to be the precise point at which Ab-Ag binding takes place. But examination of the CDR or hyper variable, regions of the variable chains in in pdb file shows that this is not the case. There are things which are better shown with simplified drawings.

We will provide viewers with examples of representations of immunoglobulins, related molecules, and relevant cellular structures ranging from conventional schematics to three dimensional and animated, as we can. Definitions, click here.

There are five classes of immunoglobulin molecules. Each class can have either kappa or lambda light chains.

Images of Immunoglogulins. Click here.

Click here for images of immunoglobulins from Xara 3D.

Development of T cells and B cells with markers in black and receptors in red.