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A theoretical analysis of experimental data is presented in this mini-review on non-random homo- and hetero-associations of cell surface receptors, which can be recruited in the plasma membrane or at the surface of the rough endoplasmic reticulum during the protein synthesis. In the latter case, the likely genetic origin of these supramolecular formations is analyzed, contrasting this concept to the mobility of the cell surface proteins. A model is offered which, on the one hand, allows the mobility in a restricted way even among microdomain-confined receptor proteins through 'swapping partners'. On the other hand, the lack of mixing molecular components of protein clusters will be analyzed, when homo-and hetero-associations are studied through cell fusion experiments. The most frequently studied cell surface patterns have included lipid raft organized HLA class I and II, ICAM-1, tetraspan molecules, IL2 and IL15 and other receptors, as well. On the contrary coated pit-associated transferrin receptors would not mix with the above lipid raft associated receptor patterns, although transferrin receptor would readily oligomerize into homo-associates. The functional consequences of these superstructures are also analyzed. On the 30th anniversary of the Singer-Nicolson fluid mosaic membrane model one has to pay tribute to the authors, because of their deep insight emphasizing also the mosaicism of the membranes in general and that of the plasma membrane, in particular.

Bare lymphocyte syndrome (BLS) is a rare immunodeficiency disorder manifested by the partial or complete disappearance of major histocompatibility complex (MHC) proteins from the surface of the cells. Based on this specific feature, it is categorized into three different types depending on which type of MHC protein is affected. These proteins are mainly involved in generating the effective immune responses by differentiating 'self' from 'non-self' antigens through a process referred to as antigen presentation. Investigations on BLS have immensely contributed to our understanding of the transcriptional regulation of these molecules and have led to the discovery of several important proteins of the antigen presentation pathway. Reviews on this subject consistently project type II BLS, MHC II deficiency as BLS syndrome, although literatures' document cases of other types of BLS too. Therefore, in this article, we have assembled information on the BLS syndrome to produce a systematic narration while emphasizing the importance of BLS system in studying various aspects of immune biology.