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Updated: Jul 17, 2026
Lipid Droplet Isolation for Quantitative Mass Spectrometry Analysis
Published on: April 17, 2017
Diversification of CD1 proteins: sampling the lipid content of different cellular compartments
V Briken1, D B Moody, S A Porcelli
1Albert Einstein College of Medicine, Forchheimer Bldg. 416, 1300 Morris Park Ave, Bronx, NY 10461, USA.
Insights
Human CD1 isoforms (CD1a-d) present lipid antigens to T cells. Their distinct cellular locations suggest specialized roles in surveying different cellular compartments for lipids, explaining CD1 gene evolution.
Area of Science:
- Immunology
- Cell Biology
- Molecular Biology
Background:
- Four human CD1 isoforms (CD1a, CD1b, CD1c, CD1d) function as antigen-presenting molecules.
- CD1 molecules uniquely present lipid antigens to T cells, playing a crucial role in immune responses.
Purpose of the Study:
- To investigate the distinct intracellular localization and antigen-presenting functions of human CD1 isoforms.
- To explore how differences in localization and function support the hypothesis of specialized roles for CD1 isoforms.
Main Methods:
- Analysis of intracellular localization of CD1a, CD1b, CD1c, and CD1d.
- Assessment of antigen presentation by CD1 isoforms in relation to endosomal acidification.
Main Results:
- CD1b and CD1d localize to acidic, late endocytic compartments.
- CD1a and CD1c are found at the plasma membrane and in early endosomes.
- Antigen presentation by CD1b/CD1d is dependent on endosomal acidification, unlike CD1a/CD1c.
Conclusions:
- Human CD1 isoforms exhibit distinct intracellular distributions and functional requirements for lipid antigen presentation.
- These differences support a model where CD1 isoforms are specialized to survey lipid content in specific cellular compartments.
- The specialization of CD1 isoforms may explain the evolutionary duplication and diversification of CD1 genes in mammals.
Abstract:
Four human CD1 isoforms (CD1a, -b,-c and -d) are now known to be antigen presenting molecules with the unique ability to present lipid antigens to T cells. CD1b and CD1d are found in acidic, late endocytic compartments, whereas CD1a and CD1c molecules accumulate at the plasma membrane and in early endosomes. Consistent with their differences in intracellular localization, most studies show antigen presentation by CD1b/CD1d to be dependent on endosomal acidification while CD1a/CD1c mediated antigen presentation is not. Taken together, recent advances in the analysis of CD1 molecules reinforce the hypothesis that the different CD1 isoforms are specialized to survey the lipid content of distinct intracellular compartments. This may help to explain the duplication and diversification of CD1 genes in humans and other mammalian species.
